When I view the site in Safari I hit a whole load of errors, but that is primarily caused by Wipr that is blocking content. It gives you an idea of potential problems though.
On Firefox it only lists the Google fonts error and there is actually a more info link that explains what is involved https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Content-Type-Options
It also shows a number of Cors related warnings for cross origin issues related to content. I have seen similar problems in the past from my Rapidweaver days related to fonts that were showing up correctly in Safari but not in Firefox and the issue was fixed at the time with an adjustment in the .htaccess file. Again there is an explanation here https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS/Errors/CORSDidNotSucceed
I would be inclined to query this with your web host as a first step and just see what they say. The basic issue is that for whatever reason your website is failing to connect with external Google sources in the correct manner. That could be down to path issues, network related or other points. I don’t think this is specifically down to Blocs or there would likely be lots of users with the same issue.
If you want to get rid if that immediate problem with the Google fonts I think you could do worse than hosting the same fonts locally, rather than trying to retrieve the CSS from Google. I always use fonts hosted on the server, rather than relying on callouts to other services and it seems to be a lot more reliable.