Please ensure the user is subscribed to the plan. Once done log the user into frontend with debug mode enabled and maximum error reporting set from Joomla global configuration. If not working appropriately you should see a fatal error upon login.
It appears the backend access checking is not entirely accurate. It will check that the path is working, but it'll also check for paths the integration does not support. Example as follows.
Writable:
/images
images/
Valid:
/images
Invalid:
images/
Please also ensure if protecting a directory under Joomlas root you need to ensure type is set to "Joomla". For example if type is set to "Joomla" and my directory is
www.example.com/site/cb/
and I want to protect the "images" folder all I need to specify is "/images".
Confirmed integration working fine.