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.
i have also tested opera now. it doesn't work properly and after logging in i'm stuck at "Log Into Rocketpot"

so logging in only works via iphone/safari and so i can use the site. all other browsers on the computer don't work... although i have no problems with all other sites. maybe it's my user/account or a special problem with a cookie on my computer?