The team is currently aware of the issues revolving around evolutions, and there is a master ticket with any and all info relating to evolutions. (https://www.pixelmonmod.com/tracker.php?p=2&t=14241
We are currently working on a full fix, however, all we can suggest in the meantime are the following:
1) Leaving the game and restarting your launcher/server.
2) Or using the /evolve command (may need to ask server admins to do this if you play on a server) if the evolution criteria have been met, and it still doesn't trigger a default evolution. This wouldn't be considered cheating, since it is a bug affecting the progression, not an official game mechanic.
Thank you for filing a report. I will lock this ticket and mark it as a "researching" as there is no "duplicate" option in the support tracker and I will also add it to the master ticket.
I will reply back if any significant progress is made with fixing the bug.