Let's Encrypt Certificate name mismatch

All looks fin in your DA and on the crt.sh too. The certificate seems to point to your ns1.liviuxxxxxx.eu hostname.

I'm no guru at this but it looks like for some reason the SNI is not working.

Try fixing your rDNS/PTR first, should be done anyway just to be sure.
Your ip is now pointing to the xx-xx-xx-hosted-by-worldstream.net and it shuold point to your hostname so ns1.liviupxxxx.eu if all is well.
Maybe that will fix things already for you.