Pi hole not blocking ads on PC, works on mobile

Yes, I'm running CentOS 8 but I didn't install Admin Console because I don't want to use it.

Pi-hole host is a VPS server, gateway was a public IP - I was following instruction and checked it twice. How it should be set?

EDIT:

I reconfigured Pi hole - now it has one internal address 192.168.5.1 but it still doesn't work.
It says:

*** [ DIAGNOSING ]: Networking
[✓] IPv4 address(es) bound to the wg0 interface:
192.168.5.1/24 does not match the IP found in /etc/pihole/setupVars.conf (Use IPv6 ULA addresses for Pi-hole)

[✗] No IPv6 address(es) found on the wg0 interface.

[i] Default IPv4 gateway: 51.38.124.1

  • Pinging 51.38.124.1...
    ping: sendmsg: Required key not available
    [✗] Gateway did not respond.

And
[root@vps817653 ~]# cat /etc/pihole/setupVars.conf
BLOCKING_ENABLED=true
PIHOLE_INTERFACE=wg0
IPV4_ADDRESS=0.0.0.0
IPV6_ADDRESS=
PIHOLE_DNS_1=1.1.1.1
PIHOLE_DNS_2=1.0.0.1
QUERY_LOGGING=true
INSTALL_WEB_SERVER=false
INSTALL_WEB_INTERFACE=false
LIGHTTPD_ENABLED=false

It says that gateway is not reachable while:
root@vps817653 ~]# ping 51.38.124.1
PING 51.38.124.1 (51.38.124.1) 56(84) bytes of data.
64 bytes from 51.38.124.1: icmp_seq=1 ttl=64 time=0.164 ms
64 bytes from 51.38.124.1: icmp_seq=2 ttl=64 time=0.414 ms
64 bytes from 51.38.124.1: icmp_seq=3 ttl=64 time=0.241 ms
64 bytes from 51.38.124.1: icmp_seq=4 ttl=64 time=0.210 ms
64 bytes from 51.38.124.1: icmp_seq=5 ttl=64 time=0.261 ms
64 bytes from 51.38.124.1: icmp_seq=6 ttl=64 time=0.217 ms
64 bytes from 51.38.124.1: icmp_seq=7 ttl=64 time=0.231 ms

What's wrong?