Hi, @onwayami2020. When you use Netlify CMS with a site at Netlify, it is using our Identity service with Git Gateway:
I’m showing two sites on this account with Identity service configured. One site has an Identity instance configured on 2020-09-30 (September 30th). However, the site with the custom domain is using a newer Identity instance configured on 2020-10-30 (October 30th).
The two instances are distinct and do not share usernames and passwords at the database level. Are you sure you added the email address and password to the new Identity instance?
If you did add the email address and password to the new instance what are the working and non-working URLs for login?
You can post the URLs publicly or private message (PM) that information to one of our support staff. I’ve confirmed that PMs are enabled for your community login. Note, that only one person can see the PM and this will likely mean a slower reply than posting the information publicly. Please feel free to reply to however you prefer though.