There is a bug that reverts iFastNet’s self-signed certificates instead of your one. That issue is relative to the SSL configuration they have. We don’t know how this will be resolved, but after some time you can access the website through HTTPS again.
Warning: Your verification URL is not returning the correct contents to our verification servers. The URL looks like it is blocking bots and which inadvertently blocks our servers from receiving the correct content. Contact your host, a professional developer or admin for further help with fixing it.
I checked the SSL section in your control panel, but there doesn’t seem to be any SSL certificate upload. You will need to generate or upload a Private Key, and upload a matching certificate, in order to use it on your website.
Let’s Encrypt is known to not work with InfinityFree. The reasons are explained in detail here: