I’ve just encountered the same bug as in this thread:
I’m SuperUser on a 2.7.1 install running on Reclaim.
I tried to delete all - which I have been able to do before - and got the “Deletion of all items was not permitted” on screen message. So I tried doing it within a collection - select all, delete, confirm delete - but the process errored out.
I got no on screen error message - I have my environment set to development in .htaccess - but when I go into the listing of processes on Job Diagnostics I see that every delete process I tried to run was listed as error.
Then I tried it again and the within collection deletes worked.