Cannot optimize

I am running Plex server Version 3.23.1 on a WD Ext2 Ultra NAS and whenever I try to optimize a video I get the message that it is optimizing, but when I check it says optimization failed and to check my settings. I have the settings at the default.
When I tried to watch a movie on a tablet, I got the message that the movie should be optimized for this device, but the server was unable to do so. I was then asked if I wanted to try to watch the original format, which fortunately worked out.
Does anyone know what I might need to do to enable optimization? As a work around I have just been using handbrake prior to uploading to the plex library on the NAS.

Thank you,

J.

Did you look at the NAS Compatability list? https://docs.google.com/spreadsheets/d/1MfYoJkiwSqCXg8cm5-Ac4oOLPRtCkgUxU0jdj3tmMPc/edit#gid=314388488.

Looks like only the WD PR2100 and PR4100 are capable of transcoding (optimizing) HD content. The DL2100 and DL4100 apparently can transcode SD content and from the notes might be able to handle low bitrate 720p HD.

The last couple of weeks, i have been having issues optimizing, it seems to get suck on 0% for a few mins then fails. If add new optimize task it sometimes works for a while then stops again.