Cloud synchronisation not working due to unavailable security certificate

[GM]

Hello,

Cloud synchronization has not been working on my Windows desktop and laptops since October 2019. When I try to sync, I get a security alert saying saying that 

"Revocation information for the security certificate for this site is not available. Do you want to proceed?"

When I click to view the certificate, I can see it was issued by "Sectigo RSA Domain Validation Secure Server CA" and is valid from 17/10/2019 (which is when I started having problems).

I have attached screenshots of the alert and of the certificate information.

Any help with this would be greatly appreciated as I currently cannot use MyLifeOrganized due to the lack of synchronisation!

Thank you,

Gianluca