I have used the new and old profile system, and I use Firefox Nightly. On one of my profiles I am unable to delete profiles created with the new profile system. When I use Manage profiles and click the delete icon I get about:deleteprofile but clicking the Delete button nothing happens. The display doesn't change, no message appears in the browser console, and the profile doesn't get deleted. This is running Firefox Nightly 153.0a1. When I use Firefox 151 on the same system (different profile) the delete works fine. When I use the same version of Firefox Nightly on a different system about:deleteprofile works fine. Both computers are running Ubuntu 24.04.4 LTS. The new profiles don't show up in about:profiles. I now have several profiles I can't delete following the instructions from https://support.mozilla.org/en-US/kb/profile-management#w_delete-a-profile . Most of them I created, closed the window, and immediately tried to delete. Following the instructions from https://support.mozilla.org/en-US/questions/1572980 and https://bugzilla.mozilla.org/show_bug.cgi?id=2000125#c4 I looked at the toolkit.profiles.storeID preference. The preference is the same in the child profiles as in the original profile. I tried starting the original profile in Troubleshoot Mode. That had no effect on the behavior.