Login page gives "Access Denied"

I’ve search thru the forums; the similar posts are years-old and say ‘problem fixed’.

New Grav installation, theme Antimatter.

Created a new user that’s identical to other users.

When attempting to log in via "…/site…/login the page returns “Access Denied”.

bin/grav logviewer shows nothing.

(There is a separate, maybe related, maybe not error. It’s a login issue with “invalid Security Token” errors logging into admin. If it continues after fixing the above issue I’ll log a separate note with all the details in the support forum.)