When I try to login to the Craft admin portal, I receive a prompt that my login credentials are incorrect, even though I am sure I have them set to the correct value.
Of note, this site is using a subdomain similar to craft.domain.com
I receive a prompt that my login credentials are incorrect, even though I am sure I have them set to the correct value.
If you're sure they're correct, then maybe Craft is connecting to a different database/Craft installation on the server than the one you think it's connecting to?
If you have access to the database, you can check to see if your user exists in the craft_users table and you can manually force a password reset like so: https://craftcms.stackexchange.com/a/13966/57
