i have tried it with firefox, internet explorer, chrome and also brave. i can't explain it to myself what it is.
since it concerns all browsers i have (and i don't use vpn oÄ.) it may have to be my provider or the firewall.
on the iphone (safari) it works. awkward but better than nothing

You should try the Opera browser, it has a built-in VPN, you can connect from the IP address of another country. Enabling VPN can help in some cases, if the problem is in the connection, you can also purchase a paid version of VPN, it works much more stable and faster. Perhaps you need to contact Rocketpot.io technical support or try to ask people who have already managed to solve this problem.