today updated Joomla 3.7.5 on 3.8.0 & I have error: "Error displaying the error page: Call to undefined method JAdminCssMenu::addChild(): Call to undefined method JAdminCssMenu::addChild()"
Joomla admin panel doesn't work with sections. Can you help me please.
Thanks a lot.
Best regards, Alex K.
Problem solved. Please, your folders (backup) on local disk (for example: C or D or E disk) upload folders on your FTP. And your admin panel again work last Joomla ver. 3.7.x