nas：ds3615xs
plex version：Plex Media Server v1.12.3.4973-215c28d86
when i went to play any movie，i got the same err： Conversion failed. A required codec could not be found or failed to install.
i had deleted pms，and deleted all folder about pms，and reinstalled ，just added one movie ，and got the same err。
logs：
May 06, 2018 19:13:20.873 [0xefe23b70] DEBUG - MDE: Cold: Direct Play is disabled
May 06, 2018 19:13:20.873 [0xe83ffb70] DEBUG - MDE: Cold: Direct Play is disabled
May 06, 2018 19:13:20.873 [0xe83ffb70] DEBUG - MDE: Cold: media must be transcoded in order to use the dash protocol
May 06, 2018 19:13:20.873 [0xefe23b70] DEBUG - MDE: Cold: media must be transcoded in order to use the dash protocol
May 06, 2018 19:13:20.873 [0xe83ffb70] DEBUG - MDE: Cold: no direct play video profile exists for http/mp4/h264
May 06, 2018 19:13:20.873 [0xefe23b70] DEBUG - MDE: Cold: no direct play video profile exists for http/mp4/h264
May 06, 2018 19:13:20.873 [0xe83ffb70] DEBUG - MDE: Cold: no direct play video profile exists for http/mp4/h264/aac
May 06, 2018 19:13:20.873 [0xefe23b70] DEBUG - MDE: Cold: no direct play video profile exists for http/mp4/h264/aac
May 06, 2018 19:13:20.873 [0xe83ffb70] DEBUG - MDE: Cold: selected media 0 / 1
May 06, 2018 19:13:20.873 [0xefe23b70] DEBUG - MDE: Cold: selected media 0 / 1
May 06, 2018 19:13:20.873 [0xe83ffb70] DEBUG - Streaming Resource: Added session 0xe9e13194:nqni3pvso9q1shkfx5b9hmjg
May 06, 2018 19:13:20.873 [0xe83ffb70] DEBUG - Streaming Resource: Reached Decision id=1 codes=(General=1001,Direct play not available; Conversion OK. Direct Play=3000,App cannot direct play this item. Direct play is disabled. Transcode=1001,Direct play not available; Conversion OK.) media=(id=1 part=(id=1 decision=transcode container=mp4 protocol=dash streams=(Video=(id=1 decision=copy width=1920 height=1080) Audio=(id=2 decision=copy channels=2 rate=48000))))
May 06, 2018 19:13:20.873 [0xefe23b70] DEBUG - Streaming Resource: Reached Decision id=1 codes=(General=1001,Direct play not available; Conversion OK. Direct Play=3000,App cannot direct play this item. Direct play is disabled. Transcode=1001,Direct play not available; Conversion OK.) media=(id=1 part=(id=1 decision=transcode container=mp4 protocol=dash streams=(Video=(id=1 decision=copy width=1920 height=1080) Audio=(id=2 decision=copy channels=2 rate=48000))))
May 06, 2018 19:13:20.873 [0xe83ffb70] DEBUG - Found session GUID of tv7lx5n5gd9gb4jr2jo5ck9a in session start.
May 06, 2018 19:13:20.873 [0xe83ffb70] DEBUG - Cleaning directory for session tv7lx5n5gd9gb4jr2jo5ck9a ()
May 06, 2018 19:13:20.874 [0xe83ffb70] DEBUG - Starting a transcode session tv7lx5n5gd9gb4jr2jo5ck9a at offset -1.0 (state=3)
May 06, 2018 19:13:20.874 [0xf03ffb70] DEBUG - Completed: [192.168.1.237:55891] 200 GET /video/:/transcode/universal/decision?hasMDE=1&path=%2Flibrary%2Fmetadata%2F1&mediaIndex=0&partIndex=0&protocol=dash&fastSeek=1&directPlay=0&directStream=1&subtitleSize=100&audioBoost=100&location=lan&addDebugOverlay=0&autoAdjustQuality=0&directStreamAudio=1&mediaBufferSize=102400&session=tv7lx5n5gd9gb4jr2jo5ck9a&subtitles=burn&Accept-Language=zh (8 live) TLS GZIP 3773ms 1155 bytes (pipelined: 3)
May 06, 2018 19:13:20.875 [0xe83ffb70] INFO - CodecManager: obtaining decoder 'h264'
May 06, 2018 19:13:20.875 [0xe83ffb70] DEBUG - HTTP requesting GET https://plex.tv/api/codecs/h264_decoder?build=linux-synology-i686&deviceId=a4bae751-0362-44e0-acf4-f8f47d6677b8&oldestPreviousVersion=1.12.3.4973-215c28d86&version=7814ac9-1285
May 06, 2018 19:13:21.863 [0xe83ffb70] DEBUG - HTTP 200 response from GET https://plex.tv/api/codecs/h264_decoder?build=linux-synology-i686&deviceId=a4bae751-0362-44e0-acf4-f8f47d6677b8&oldestPreviousVersion=1.12.3.4973-215c28d86&version=7814ac9-1285
May 06, 2018 19:13:21.863 [0xe83ffb70] DEBUG - HTTP requesting GET https://downloads.plex.tv/codecs/7814ac9-1285/linux-synology-i686/libh264_decoder.so
May 06, 2018 19:13:34.287 [0xf0111b70] DEBUG - handleStreamRead code 335544539: short read
May 06, 2018 19:13:34.481 [0xf03ffb70] DEBUG - Auth: authenticated user 1 as myhcloud
May 06, 2018 19:13:34.481 [0xeb3ffb70] DEBUG - Request: [192.168.1.237:55905 (Subnet)] GET /player/proxy/poll?deviceClass=pc&protocolVersion=1&protocolCapabilities=timeline%2Cplayback%2Cnavigation%2Cmirror%2Cplayqueues&timeout=1 (5 live) TLS GZIP Signed-in Token (myhcloud)
May 06, 2018 19:13:34.481 [0xeb3ffb70] DEBUG - Beginning read from two-way stream.
May 06, 2018 19:13:42.955 [0xe7bffb70] DEBUG - Request: [127.0.0.1:43469 (Loopback)] GET /library/changestamp (6 live) GZIP Signed-in Token (myhcloud)
May 06, 2018 19:13:42.955 [0xf03ffb70] DEBUG - Completed: [127.0.0.1:43469] 200 GET /library/changestamp (6 live) GZIP 0ms 463 bytes
May 06, 2018 19:13:54.483 [0xf03ffb70] DEBUG - handleStreamRead code 335544539: short read
May 06, 2018 19:13:54.665 [0xf03ffb70] DEBUG - Auth: authenticated user 1 as myhcloud
May 06, 2018 19:13:54.665 [0xeb3ffb70] DEBUG - Request: [192.168.1.237:55914 (Subnet)] GET /player/proxy/poll?deviceClass=pc&protocolVersion=1&protocolCapabilities=timeline%2Cplayback%2Cnavigation%2Cmirror%2Cplayqueues&timeout=1 (5 live) TLS GZIP Signed-in Token (myhcloud)
May 06, 2018 19:13:54.666 [0xeb3ffb70] DEBUG - Beginning read from two-way stream.
May 06, 2018 19:14:14.668 [0xf0111b70] DEBUG - handleStreamRead code 335544539: short read
May 06, 2018 19:14:14.856 [0xf03ffb70] DEBUG - Auth: authenticated user 1 as myhcloud
May 06, 2018 19:14:14.857 [0xe7bffb70] DEBUG - Request: [192.168.1.237:55923 (Subnet)] GET /player/proxy/poll?deviceClass=pc&protocolVersion=1&protocolCapabilities=timeline%2Cplayback%2Cnavigation%2Cmirror%2Cplayqueues&timeout=1 (5 live) TLS GZIP Signed-in Token (myhcloud)
May 06, 2018 19:14:14.857 [0xe7bffb70] DEBUG - Beginning read from two-way stream.
May 06, 2018 19:14:14.966 [0xe83ffb70] ERROR - Error issuing curl_easy_perform(handle): 28
May 06, 2018 19:14:14.966 [0xe83ffb70] DEBUG - HTTP simulating 408 after curl timeout
May 06, 2018 19:14:14.966 [0xe83ffb70] ERROR - Codecs: Download failed: Failed to download 'https://downloads.plex.tv/codecs/7814ac9-1285/linux-synology-i686/libh264_decoder.so': 408
May 06, 2018 19:14:14.966 [0xe83ffb70] ERROR - Error configuring transcoder: Decoder install failed: h264
May 06, 2018 19:14:14.966 [0xe83ffb70] DEBUG - Streaming Resource: Terminated session 0xe9e13194:nqni3pvso9q1shkfx5b9hmjg with reason Conversion failed. A required codec could not be found or failed to install.
May 06, 2018 19:14:14.966 [0xea3ffb70] DEBUG - Killing job.
May 06, 2018 19:14:14.966 [0xea3ffb70] DEBUG - Job was already killed, not killing again.
May 06, 2018 19:14:14.966 [0xea3ffb70] DEBUG - Stopping transcode session tv7lx5n5gd9gb4jr2jo5ck9a
May 06, 2018 19:14:14.967 [0xe8bffb70] DEBUG - Cleaning directory for session tv7lx5n5gd9gb4jr2jo5ck9a (/volume1/Plex/Library/Application Support/Plex Media Server/Cache/Transcode/Sessions/plex-transcode-tv7lx5n5gd9gb4jr2jo5ck9a-9b30a874-a750-41a0-8155-ec7939c7fde9)
May 06, 2018 19:14:14.967 [0xf03ffb70] DEBUG - Completed: [192.168.1.237:55899] 404 GET /video/:/transcode/universal/start.mpd?hasMDE=1&path=%2Flibrary%2Fmetadata%2F1&mediaIndex=0&partIndex=0&protocol=dash&fastSeek=1&directPlay=0&directStream=1&subtitleSize=100&audioBoost=100&location=lan&addDebugOverlay=0&autoAdjustQuality=0&directStreamAudio=1&mediaBufferSize=102400&session=tv7lx5n5gd9gb4jr2jo5ck9a&subtitles=burn&Accept-Language=zh (5 live) TLS GZIP 55815ms 452 bytes (pipelined: 1)
May 06, 2018 19:14:15.031 [0xea3ffb70] DEBUG - Transcoder: Cleaning old transcode directories.
May 06, 2018 19:14:15.031 [0xea3ffb70] DEBUG - Whacked session tv7lx5n5gd9gb4jr2jo5ck9a, 0 remaining.
May 06, 2018 19:14:16.038 [0xf0111b70] DEBUG - Auth: authenticated user 1 as myhcloud