Changed Xfinity email password won't work on more than one Apple device

Hi. I changed my Xfinity email password through Safari on my iMac. I was able to login to Xfinity on my computer using Safari and to get my email in Apple/Mac Mail on my computer. However, I wasn't able to get my email on my phone or login Xfinity using Safari on my iPhone. I spoke with customer service at Xfinity and they had me re-change my Xfinity email password using Safari on my iPhone. I was able to do this, login to Xfinity on Safari on my iPhone and get my Xfinity email on my iPhone... however, I was no longer able to do the same on my iMac. Spent more time on Xfinity customer support only to have them tell me it's an Apple issue. Can someone please help????