I tried to update one of my Kirby installations from 2.1 to the most recent version 2.4.1, which worked fine on the front-end. I was not able to access the panel, though, getting redirected to the /panel/login/ page with each attempt and with any user.
Changing the PHP version from 5.6.x to 7.0.x did not help, neither did to HTTPS, nor the implementation of a session fingerprint via config file, as described here – all of which without any clues from the error log.
What worked, oddly: switching to the second most recent release, 2.3.2.
Is this a common issue with Kirby CMS 2.4.x? What might be the cause?
Thanks in advance for any kind of help, and