Server Version#: 1.40.0.7998
Tried to upgrade to this on MyCloud Pro PR4100 from build 1.32.8.7639. Instead of Completed, final message is App Installation Faiure. I was able to reinstall build 1.32.8.7639 successfully. I have a Terramaster server and was able to upgrade it to 1.40.0.7998. My three WD MyCloud servers still function and still serve content, but none of them will upgrade.
SOLUTION: I installed this build as a reinstall. With previous upgrades, I would remove the app entirely and install the new version over “nothing at all.” This time I simply shut down service (toggled the Run App switch to OFF), then installed the new version on top of the old - per the now-standard recommendation. Results: success. I also made sure to install on one server at a time, instead of three at once.
I have the same exact MyCloud Pro PR4100 with build 1.32.8.7639 (last working version for my box). I tried to update to build 1.40.0.7998 while it was running and not running as you suggested. And it would fail to connect to my Plex library. Luckily I have build 1.32.8.7639 bin saved so I just reverted back to that build and it worked again. But I am not sure how to update this app anymore (not going to full reinstall it and lose all my metadata / settings). Please help 
You make it sound as though you have a different problem. My problem was that I would get a message saying that the application installation itself had failed. I managed to get past that, and my servers connect to my Plex account with all libraries intact. If your libraries don’t even show after you install the new build, you’ve got a worse problem than I have ever had. You might want to start a new topic and go through the exact steps you took. That will be the only way you can get the attention of a Plex employee.
