We use ManageWP to sync and backup our sites.
A recent update to the "Ultimate Branding" plugin appears to have caused a conflict with our ability to "Connect" our site via the ManageWP worker plugin to ManageWP.
If we try to reconnect our site to ManageWP with Ultimate Branding enabled, we get the message .. as follows:
Fatal Error (E_ERROR): Call to a member function get_current_tab() on null occurred in wp-content/plugins/ultimate-branding/ultimate-branding-files/classes/class.ub.helper.php on line 34 please make sure that your website is accessible
I have contacted ManageWP .. they in turn, say to contact WPMUDEV as it looks like a conflict with Ultimate Branding.
For now I have disabled the Ultimate Branding plugin and the site connects/syncs properly with ManageWP.