After a long time on the phone to my host (Siteground), it occurred to me that it might be Admin Tools, as my subscription had expired. When I disabled Admin Tools (renaming main.php to main-disable.php), the issue was resolved - I could get in.
I therefore thought Akeeba Admin wasn't working because my subscription had expired, so I paid to renew my subscription. I installed the new version and.... now I still have the same problem as before. I can't log in because the server won't respond. When I disable Akeeba Admin I can log in.
So I currently have it disabled.
Could you please let me know what I can do to get Akeeba Admin working again?