Unable to send email from icloud Account on iPhone & Mac

Hi,

Roughly a month ago, I started receiving a message saying that my username or password for "iCloud" are incorrect, with either OK or settings button. I tried signing out of icloud, and changing my iCloud password, however this hadn't resolved the issue, so I tried restoring the phone.

I also recently (just over a month ago) purchased a 16-inch MacBook pro, which is also expericing the same thing. Given that I can still send email through the icloud webmail, I'm not completely stuck, but I dare say I'm going to have to contact Apple support, but thought I'd just post this up in case anyone has any suggestions first.