Website Error

Good day! I am receiving this error "ERR_SSL_VERSION_OR_CIPHER_MISMATCH" when attempting to open my website. It is not only showing for me but also for our students. I was made to understand that I need to acquire a SSL certificate to fix this issue but I am not sure how to go about the process. I did see an 'Activate SSL' when I visited the domaine tab but it is saying this:

"Domain cant be verified as it doesn't exist on builder"

Can you assist me?