Sorry to write the bug report here, but my bug report by email came back reason flagged as spam
I'll make it simple:
If you move a category, please watch out where to move it,
Do not move it into "itself". In this case in the mysql database, table mgr_categories one can see the category has the same number as its "parent" e.g. ID, parent - 2 , 2
This causes the category to not show anymore in maian greetings. Not in admin, not in the site.
The Workaround solution if one has this for now, is to manually in table mgr_categories change the parent category, e.g make it 2, 0 but not twice the same number.
I hope this can be of help.