Hi, I did have a look at your site but I can’t see any particular issues. Is this happening on a particular browser or particular operating system? Clearly it does work but there could be certain combinations that don’t (like old operating systems).
Protocol errors suggest that the client (your browser) can’t talk to the server. I note that your certificate RSA keysize is 4096, and you have many subject alternative names on the same certificate, that’s the only [slightly] unusual thing I can see. Basically, your certificate is fine but your client software/OS may not be.