I have one installation of Magento working in it's own DocumentRoot. I have another installation of Magento working in it's own DocumentRoot
Both webroot are on the same server; so they both have the same IP, yet they have different domain names.
I can visit each frontend successfully, but I cannot login to both admin panels at the same time. I'm constantly reading about it being a cookie issue, but even after clearing my cache, cookies, sessions... I still cannot login to them both simultaneously.
Why is this happening? The two installations are completely independent of one another, they both use a different database. I simply cannot understand this and it's very frustrating.
When I say that I cannot login, I mean that the login page does not log me in. I receive no error or anything; I'm just redirected to the login page again.
As a user brilliantly pointed out, and I forgot to mention it, but I do have an SSL cert for the domain assigned to the IP.
I'm not sure how it worked, but I cleared all my cookies and cache, closed the browser and waited for everything to be released from the memory; like how you wait for a router to discharge after unplugging it and before replugging it. I opened the browser (Chrome) in normal (not incognito mode) mode, opened both admin login panels in separate tabs, and it worked?
Given this new odd discovery that I haven't tried to replicate yet, I know that it is indeed possible to be logged into both panels; even when using the same IP.