enabling signup users manually.. is it possible?

Hi,
I wonder if the following scenario is possible:

1.user is signing up using the sign up page
2.user is not redirected to paymant gateway but to default login page
3.UM admin applies manually a profile to the user
4.user is now able to login

I tried this but no success.
After sign-up the user is present in the user list, with no valid profile assigned to him . all ok till now

Next, the UM admin(customer) gives the user a valid profile, everything seems ok but
when the user is trying to login the response is : user not found

Any ideas?