The site has worked fine except for admin tools.
When I try to login to the admin I just get 'spinning wheel' and the connection never resolves.
If I disable Admintools (renaming the plugin) everything works fine.
I have replaced the htaccess files with the standard joomla in the front-end and then used 'password protect administrator' on the admin and all works fine as long as admintools is disabled, but just spinning if it is enabled.
I have also gone through the WAF and attempted to disable all the protections and then renable admin tools but still get the 'spinning wheel'.
I have also run all the admintools 'tools' (fix permissions, temp log directory check, etc,)
In my server error logs the only thing that I've seen reported is this:
[Sat Dec 08 10:34:14.108894 2018] [:warn] [pid 9793] [client xx.xxx.xxx.xxxx;55844] Timeout waiting for output from CGI script /home/MYWEBSITE/public_html/administrator/index.php, referer: https://MYWEBSITE.org/administrator/index.php?option=com_admintools
No errors are noted in the console, just a 'spinning' web site.
The front end is working fine (with admin tools on or off).
I've migrated over a dozen sites this way to this new server and not had any problems (although this is a bit more complex config than most others).
Any ideas where to look to track down the problem?