Only the ports that are listet on the pool page -->
https://solo.ckpool.org/mybe you need a special firewall rule in your hosting location and ck pool is on a blacklist (from network view).
Can you open a shell and try a ping?
ping -4 solo.ckpool.org
Ping wird ausgeführt für solo.ckpool.org [51.81.56.15] mit 32 Bytes Daten:
Antwort von 51.81.56.15: Bytes=32 Zeit=103ms TTL=53
Antwort von 51.81.56.15: Bytes=32 Zeit=104ms TTL=53
Antwort von 51.81.56.15: Bytes=32 Zeit=104ms TTL=53
Antwort von 51.81.56.15: Bytes=32 Zeit=101ms TTL=53
No problems from the UK either
64 bytes from solo4.ckpool.org (51.81.56.15): icmp_seq=1 ttl=50 time=86.3 ms
64 bytes from solo4.ckpool.org (51.81.56.15): icmp_seq=2 ttl=50 time=81.5 ms
64 bytes from solo4.ckpool.org (51.81.56.15): icmp_seq=3 ttl=50 time=94.5 ms
64 bytes from solo4.ckpool.org (51.81.56.15): icmp_seq=4 ttl=50 time=82.7 ms
64 bytes from solo4.ckpool.org (51.81.56.15): icmp_seq=5 ttl=50 time=81.6 ms
64 bytes from solo4.ckpool.org (51.81.56.15): icmp_seq=6 ttl=50 time=81.9 ms
64 bytes from solo4.ckpool.org (51.81.56.15): icmp_seq=7 ttl=50 time=83.3 ms
64 bytes from solo4.ckpool.org (51.81.56.15): icmp_seq=8 ttl=50 time=81.3 ms