Hi all, I have multiple iMacs and changed my apple id all my devices except one. It is still using my old id and it wont let me login. I tried using the old password related to that old id and it still doesn't work. How can I change my apple id associated with that computer? The old id is unusable. I went on to the the apple id site and didn't see anything.
Someone please help.
iMac (27-inch Mid 2011), OS X El Capitan (10.11.6)