Does anyone know why when I login to any of my EE sites at admin.php I have to login twice? The first time it just reloads the page and I have to login a second time to access the backend?
I've had that happen, generally when a session string is automatically added to the admin url, so when it looks like:
Generally, if it's without the session data, the login happens fine, the first time; but with it seems to break then re-trigger the session info by forcing the second login. I don't know why it happens, but that's my situation.
I counteracted by making sure my bookmark and history brings up the clean reference first:
Then its the first time, all the time, for me. It could work for you. First step, is go to your browser history and delete all the history files that have session ids attached to them. Just leave a bookmark and a history item of the clean domain control panel access.
This prioritizes that url when you start typing. Hopefully, that will work for you as well.