Thank you for posting. This error is very similar to another issue we are looking into. It is sometimes caused by a change in wireless networks. Did you recently log into a different wireless network? We are working on a solution for this issue. In the meantime, if you quit and restart TheBrain each time you change networks (going from home to office for example), it should work properly for you. Sorry for the inconvenience.
Another option you can try is modifying the endpoint for syncing. Please click on File > Utilities > Manage Endpoints... Click on TheBrain Cloud > Edit and change the address to: https://api.thebrain.com/
You'll need to save this edit and restart TheBrain for this change to take effect.
If this does not resolve the problem for you, please let us know. We still have more options and I'm confident we can get you connected to your cloud account again.