I got tired of retyping this so am posting a new thread I can link to later.
Often when one encounters a problem with OH, particularly after an update, OH will refuse to run or certain parts of OH stop working. Some reported errors include:
- 500 or 404 errors when accessing the UIs
- lots of exceptions from Jetty or other core components in openhab.log
- OH refuses to start at all
The first step in debugging the problem is to clear the tmp and cache.
Stop OH if it is running.
Delete the contents of /var/lib/openhab2/cache and /var/lib/openhab2/tmp. For manual installations these folders are in your OH home folder under userdata. DO NOT DELETE THE FOLDERS THEMSELVES, JUST THE CONTENTS.
Watch openhab.log for errors, test if the problems persist. If so, search the forum and post a new thread if you do not find your solution.