Basically the force password reset doesn’t work with customised login system such has UM, so you need to unset this flag. See https://wordpress.org/support/topic/unset-the-force-users-to-reset-their-passwords-flag/#post-15938364 for details.
I believe I found it. Running the following SQL statement seems to solve the issue:
delete FROM wp_usermeta where wp_usermeta.meta_key=’acui_force_reset_password’
