I'm having a lot of problems with my server after updating to 7.6. If I login with the "keep me logged in" option enabled, it immediately goes back to saying I'm not logged in. If I have that option off, it lets me log in, but if I then click on the control panel link it says "You must have the proper permission to access this area." and then takes me back to the main page with me still logged in. Occasionally, for some reason, I can actually log in and get to the control panel, but I haven't spotted the pattern to it working, but it's like one in a hundred.
In addition, both I and my users have been getting the following error when trying to post anything:
"The host from which you are accessing the board is not recognized as a valid host. This is more than likely related to a firewall issue that is blocking the referer variable. Check your firewall settings and try again."
7.5.x was working fine, and I don't think anything else has changed at my end. I'm not aware of any firewall that could be causing this problem for everybody. I'm using the latest Safari on macOS and iOS, happens on both.
Forum is at http://tla.systems/ubbthreads/
Any help appreciated!