This is the mistake when creating a category - An error has occurred. 0 Call to undefined function utf8_strtolower()
it is impossible to create even a category please help
"The PHP error
"Fatal error: Call to undefined function utf8_strtolower()" typically occurs because the necessary multibyte string extension (mbstring) is either not installed or not enabled on your server. "
You are probably using Joomla 6.0. Virtuemart is not yet compatible with J6. utf8_* functions have been removed in J6. Their usage needs to be replaced with Joomla\String\StringHelper::strtolower() or mb_strtolower().
https://dev.virtuemart.net/projects/virtuemart/repository/virtuemart/revisions/11259/entry/trunk/virtuemart/administrator/components/com_virtuemart/helpers/vmtable.php#L1740
https://dev.virtuemart.net/projects/virtuemart/repository/virtuemart/revisions/11259/entry/trunk/virtuemart/administrator/components/com_virtuemart/views/userfields/view.html.php#L177
Interesting, so far I see I replaced that in vm5.