Hi Valodia,
The most common reasons this seems to happen have to do with users enabling settings that they are not set up to support. For example, engaging the "Require SSL for administrator functionality" or the "Limit Administrator functionality by IP range" settings available in the security panel. If you've turned on the SSL requirement for example, but your site is not deployed with a proper SSL certificate and you're trying to access it via a typical HTTP connection, then you'll see this kind of loop back to the homepage. See:
I've included an example query in our documentation on how you can use SQL to check the current SSL setting, and turn it off if needed. See:
I've also shared an example in the user forum on how to do the same thing with the IP range restrictions, here:
If you can't remember your MySQL credentials used during installation, or aren't sure how to access the MySQL command-prompt, I've covered that in our documentation as well:
The other thing you could check is whether or not you've set your entire site into read-only mode. This is managed via one of AtoM's configuration files. See:
Finally, it could be that your Admin account was set to inactive, or there's some other problem with the account itself. You can try creating a new Admin account from the command-line, so you can log in with it and check the settings on the current account. If you can log in with a different Admin account, then the problem probably has to do with the original user account. If you can't log in with a new Admin user, then it's likely one of the issues above - or else a problem with the permissions settings for the Admin group as a whole. To create a new Admin account from the command-line:
I suggest that you start by checking whether or not any of these are the cause, and if the instructions provided above help you to resolve them. If not, please let us know what you find. The last possibility that occurs to me off the top of my head has to do with missing dependencies, or different versions of them. We develop, test, and typically release AtoM on Ubuntu LTS releases, and usually recommend Linux virtualization if installing on a Windows server. I'm not sure if that's what you've done here or not, but if you've deviated from our recommended installation instructions, it's possible that some critical dependency or tool version is different or missing, and this is causing issues with authentication.
For now, let us know what you find, what you tried, etc. and we can go from there.
Cheers,