Imap broken or works 1 or 2 times a day

Something os broken with Xfinity imap servers.  My e-mail on my iPhone, iPad and MacBook with Thunderbird does not sync properly.  All 3 devices were working properly and nothing has changed on any device and I have checked my internet connection.  A few times per day one of my devices will sync, but the others do not.  Something had changed with Xfinity's imap servers to cause them not sync reliably  Hopefully there is an easy fix.