SQL claims users do not exist when they do.

I wanted to grant access to a table to a user so I exeuted this:

Which returned this message:
Cannot find the user 'MyUser', because it does not exist or you do not have permission.

I then ran this:
EXEC sp_change_users_login @Action='update_one', @UserNamePattern='MyUser',    @LoginName='MyUser';

Which returned this:
Terminating this procedure. The User name 'MyUser' is absent or invalid.

I am logged in as 'sa' and 'MyUser' is a valid SQL user.

I have checked other SQL users and they fail the same way.

What is wrong here and do I fix this?
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

Brian McDonaldIT ManagerCommented:

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
rwheeler23Author Commented:
EXEC sp_change_users_login 'report'  Returns no users

I just tried the GRANT command again and it worked. The difference now is most users have gone home and the load on this old server is much lighter.
Brian McDonaldIT ManagerCommented:
If they were in the system it'd probably block adjustments to their user permissions, because of active use. So that makes sense.
rwheeler23Author Commented:
A more accurate message would have been helpful.
rwheeler23Author Commented:
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.