After upgrading Akeeba Backup Pro to 5.5.0 I get an error 500. I checked my error log and see the following:
PHP Fatal error: Call to a member function addStyleDeclaration() on null in /var/www/vhosts/44/467930/webspace/httpdocs/new.thegaslampgallery.com/plugins/system/backuponupdate/backuponupdate.php on line 230
I followed the instructions in the documentation ("The installation / update broke my site!") which allowed me admin access once again, then I tried to re-install Akeeba Backup Pro 5.5.0 but it fell over with the same PHP Fatal error as above.