Hello!
I switched on Joomla debug, and now I see more:
An error has occurred.
0 Cannot use object of type stdClass as array
/web/salibafiligree/salibafiligree.com/plugins/content/vpadvanceduser/vpadvanceduser.php:122
So the problem is with VP Advaned User plugin. There is an update for this plugin, so maybe updating it can solve the issue. I will update next week and will see if it helps or not. If I will have problems after updating, I will report it here. For now thanks for your support.