Edit:
Just saw you post about your own addon... A hint would have been nice. Moved to lua/XML forums
Ideas that always help:
Disable all other addons and test if it works or not.
If it works: Other addon was the reason, find out which one.
If it does not work: Describe STEPS 1 after another, from reloadui to error/problem, how to reproduce this.
Check with LibDebugLogger and DebugLogViewer (shows you LibDebugLogger entries and loaded addons, error messages before chat is ready so which you normally do not see then!) if there is any error mesasge at current UI load (left top edge of DbeugLogViewer -> change dropdown to "current ui load" or similar).
Enable Debug stack traceback in DebugLogViewer addon settings menu so see where the code was read from (stack) as the error happened, if you click on the error entry in ebugLogViwwer.
Find out that way what happens and fix it, OR post the DebugLogViewer stack entryw ith all variables and error messages and/or share the LibDebugLogger file (do a reloadui after the error happened to save it to disk properly!!!) at
https://sir.insidi.at/or/logviewer/ so we can have a look at it, see loaded addons and versions etc.
Everything else would be a try and error and waste of time.