Important for network debugging
systemctl restart networking
then tests like
For different domain providers (my case is porkbun, don't forget to enable API access on domain manager), look here: https://github.com/acmesh-official/acme.sh/wiki/dnsapi2 (also check web GUI's: ACME>Challenge Plugins> Add>DNS API drop down menu for your DNS)
Securing Proxmox (Source)
Note: I had the "This site can't be reached"