After waiting ~15 hours for a reply from customer support, I was told this was likely due to PDO not being setup on the server (something that could of easily been checked since they had full access)... which is indeed already setup, so no solution as of yet.
Go to the install directory (/install) and that will pull up the install process. I had this same issue, however the install did not work for me (waiting on support for almost 6 hours now to help me out).
When upgrading to the new version, I uploaded all of the files over my existing installation (after making backups).
When running the install I get to step 2, which says I am running an old version and it will be updating it to v6. If then provides no button to get to the next step.
Anyone else have this issue?
I'm having the same issue; user area does not work for me. It seems to be any whmcs.com using a https url does not load. It's funny because I can't post to support at all, because those urls are all using https, so they return an error:
This webpage is not available
I can access it via my phone (cellular data) -- but not on any of my computers.