Sign in to change the store links, logo or wording.
Ask another admin to reset it for you from the Users section. If no admin can get in, recover from the server over SSH — there is no email reset, because this page has no mail configuration and a self-service reset would be a way in for anyone:
cd /var/www/arcsstore
sudo -u www-data php reset-login.php username 'newpassword'That creates the user if it does not exist, resets the password if it does, and clears any lockout.