If you have "SSL tracking" enabled, you are likely to see "SSL certificate change" errors regarding Office 365 accounts.
Not a bug, rather working as expected, although annoying.
Microsoft *is* apparently in the process of updating Office 365 SSL certificates, so Aqua will be detecting the change and asking you to confirm.
But here is the annoying part: since there are many, many actual servers behind Office 365 (office365.outlook.com) and they were not all updated at the same time... the error may come up again and again asking you to confirm each time.
It's just Aqua running into different actual (loaded balanced) servers, and their certificates not being in sync.
To avoid the nuisance, you can turn off Aqua settings -> network -> SSL tracking, maybe for a few days (if you know that you won't be connecting to some random, potentially malicious, networks).
Or keep it enabled for better security, but you will have to keep confirming until MS is fully done with the update.