Could you please confirm that the ip of that server is 35.173.69.207 ?
I contacted the myqtthub site support team, and here is their answer:
<<We have been checking IP reported and it is not blocked and was not blocked in the past:
[Estado de black list para 35.173.69.207]
IP 35.173.69.207 NO está actualmente listada/bloqueada
[Estado de lista blanca para 35.173.69.207]
La IP 35.173.69.207 no está actualmente en lista blanca
No se encontraron registros en el histórico para 35.173.69.207
No se encontró actividad para esta IP [35.173.69.207] en el log [/var/log/mail.log]
No se encontró actividad para esta IP [35.173.69.207] en los registros WEB
We are also able to ping from mqtt nodes to this ip without any problem (which will not
be possible if there were a blocking rule in place):
ping 35.173.69.207
PING 35.173.69.207 (35.173.69.207) 56(84) bytes of data.
64 bytes from 35.173.69.207: icmp_seq=1 ttl=47 time=85.4 ms
Possibly there is a block or firewall that is not allow your client application to connect
to node02.myqtthub.com over port 1883/tcp on your side?
Your code is right and it is supported (as you was able to check from other locations).
Check with pythonanywhere.com what could be happening with outgoing traffic to reach our side...
Best Regards,>>