the fix would only be restart the service when you back to netcut . so you should work your setting and Jailed computer when netcut service is running.
when you hide netcut UI, and it been killed by the android system. we can not do much on this part. are you ok with this?
Do you have some kind of firewall block netcut access arcai.com ? if so, it might forbid your login in success.
Also, try to uninstall , reboot, then reinstall. in case you have crupted account data file. that will recreate the account data file when you relogin in.
Can you provide a screenshot of the error when you login?