I've had Office 365 on my iMac for 2 yrs, it's not expired, and just this week, it requires me to re-activate every time I re-boot my iMac. This is crazy waste of time and I need to go in and deactivate one of my 5 subscriptions so I can re-add it in order to check my Outlook and use the products. I'm on an iMac on Safari. Please advise how to fix ASAP.