The problem is that you require a password reset and, I presume based on context, have MFA enabled on this user. This creates a condition where MFA wants to validate the user's login by redirecting to the captive page, but the password reset wants to redirect to the user edit profile page to change the password. This causes a redirection loop. Supposedly, Joomla 5.2.3 fixed this… but they only did so in the frontend.
You should also report this problem to Joomla's issue tracker, so they can fix it.
In the meantime, let's help you out.
You will need to visit the /index.php?option=com_users URL on your site to see the frontend login page. Log into the site's frontend like that, and you will be able to reset the password.
If this is not possible because that's a Super User and you have disabled backend users login into the frontend in Admin Tools, you may want to log into the site as a different Super User, temporarily disable this feature and retry.
If you don't have a secondary Super User account and the only other Super User left can't figure it out, have them create a Temporary Super User for you in Admin Tools. Use the temporary Super User to log into the backend, remove the required password reset flag from your user account, log out, log in with your Super User, and change your password, then remove the Temporary Super User.
Assuming the Super User account was forced to do a password reset as a result of Admin Tools' forgotten Super Users feature, go to Configure WAF, Hardening Options and scroll down to “Protected users“. Click on the plus sign button, then select your Super User account from the list. This will ensure that your Super User won't be forced to require a password reset in the future. Best do this on all of your clients' sites for both yours and their main Super User accounts.
Nicholas K. Dionysopoulos
Lead Developer and Director
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