This site can’t be reached - How to fix

I receive this message when logging into my website - Not sure how to fix or which certificate to request a refresh of

This site can’t be reached

The webpage at XXX might be temporarily down or it may have moved permanently to a new web address.

ERR_CERT_AUTHORITY_INVALID

As a side note - I only just switched to Cloudflare and am thinking of switching back to google registry where my site did work.