We just upgraded the QV installation from SR11 to SR15 (removed the old version and installed the new one) without touching any thing else. The server is not a new machine and I've checked all settings several times.
I would inform you that the issue is resolved. Some users who were server administrators (inclusive myself) were able to log on the AccessPoint from outside of the server. All users were able to log on the AccessPoint when they were on the server.
So I thought that this issue should be an authentication problem. So I added some users to the IIS_IUSERS group and edited the permissions for the Application Pool and the QlikView site in IIS, so IUSER was granted access to the site. It resolved the issue.
The concerned environment is a DEV environment. We are going to upgrade the customer's PROD environments as well very soon.
The question is what will happen when we go forward to the PROD environments. Should we do the same there and why? Does it make sense at all, that IUSER group must be granted access in IIS?
It is not the case currently in customer's PROD environments.
We are operating with IIS 8.