PROBLEM: The FileMaker SSL certificate for your cloud instance does not cover your FileMaker Cloud root address.
How are you handling redirects to FileMaker Cloud, given the new browser restrictions?
You want to give your users a simple URL, such as https://data.yourdomain.com.
Sure, you can set your DNS to redirect from this domain to your FM Cloud domain.
Yet, each of these destinations has a problem:
Address 1 takes the user to your FM Console login. Not what you want.
Address 2 takes the user to the web interface. This is what you want. But DNS does not permit you to redirect to a path; you may redirect only to a FQD.
Address 3 is the root address of your FM Cloud instance. It does the trick.
However, all browsers have begun refusing to open the root address. They complain that it doesn't have a proper SSL certificate. Hmmm. Your FM Cloud instance does have a proper SSL certificate. This redirect did work for the past couple of years. It stopped working last month, with the introduction of this new browser behavior.
So, redirects are no longer possible.