Q: logging into iTunes with updated email

iTunes Account- I had to change my email address, managed to do all this on my iPhone,Macbook etc, but cannot complete the process on my iMac!!  Wheel has been spinning for an hour!!!  I guess its frozen.  I l

- I Logged out, then logged in, accepted that it would loose stuff from icloud, then logged on, Nothing.

Any suggestions PLEASE?

Thanks in advance