Unable to login to my sub domain login page

You could try to set the password directly in the database. You can find instructions here: https://www.ads-software.com/support/article/resetting-your-password/#through-phpmyadmin

Note that in a multi-site installation there are several users tables in the database. You have to find the one that is used by each sub-site. You can see this e.g. in the options table at the siteurl there or at the records in the users table itself.