hey @RGaskin thanks for your request and for supporting the snap,
without your logs we’re guessing, see How to manage Nextcloud snap logs and also how to run the debugging script
see also Getting help
if that log file is too large, you can try truncating the log sudo truncate -s 0 /var/snap/nextcloud/current/logs/nextcloud.log and then restart the snap which writes a brand new log. that shouldn’t be too large. see How to manage Nextcloud snap logs
reading logs is something for devs… for us non-devs it’s 0's and 1's like in the matrix 
. some folks read logs like we read a novel. its basically hit and miss and I’m merely the documentation and support guy 
what could help though is since when you’ve had this issue:
- was it due to a recent upgrade? see How to revert Nextcloud snap after failed update
- did the issue occur after installing an app?
- which app did you install last?
- did the issue occur after changing some configuration parameters?
- which parameters did you change?
relax, take a deep breath, get a cup of tea and consider your options. recollect steps taken, note recent changes and structure that information. do the basics and try to get a grasp of the situation.
you’re on the right track and doing a good job… consider develop and contribute
looking at your app list (well done for posting that) you have some third party apps installed that rely on binaries which are not packaged in the snap see 3rd party app incompatibility and confinement
Nextcloud assistant requires executable binaries that are not packaged in the snap… so disabling the assistant app should solve your issue.
sudo nextcloud.occ app:disable assistant
see
other apps you’ve installed that could cause an issue:
- collectives (not causing issues on some of my installs)
- circles (changed to teams, works fine after disabling/re-enabling)
- drawio (not causing issues on some of my installs)
- tables (unknown, never tried)
- timemanager (unknown never tried)