Unable to connect outlook to Office 365 since reboot

Hi. I am using Parallels desktop 11 for several years with a Windows 7 guest. Suddenly after a reboot yesterday I am now unable to connect to Office 365 from Outlook 2016 and also have a desktop remote client called Splashtop that can't connect to it's servers. However the internet appears to be working fine.

Things I have tried are:

• changing between shared and bridged network (no difference)
• Window 7 system restore
• Changing location (ie connecting to a different network)
• Updated to the latest version of Parallels 11
• Removed and reinstalled Parallel Tools.

I've completely run out of ideas and would appriate any help or advice that anybody could give.
Many Thanks
Matt

 

Some more information. I have run the Microsoft Support and Recovery Assistant for Office 365, and the result says this:

Office 365 SSL Cert Validation Failed
We've detected the Office 365 SSL certificate is not trusted on your device. Please contact your administrator for further assistance

 

Please follow steps in this article and check the issue.

 

Since the problem is related to the Outlook client connection, please check login if the network environment is well the problem occur.

 

Choose Account Settings > Account Settings. On the Email tab, choose your account (profile), and then choose Repair. Note: The Repair option isn't available if you're using Outlook 2016 to connect to an Exchange account. Follow the prompts in the wizard, and when you're done, restart Outlook.

Regards,
Peter