Ok, still not clear, but lets proceed… groov uses https, so it has to be an encrypted connection, this means it uses a certificate, out of the box its a selfsigned one. This is why your browser is showing you the warning (warning, not error). Your browser can not look up its certificate trust store and verify the certificate.
For now, accept the warning and log in (or create your first account).
Once you are using the groov Manage pages you can export the certificate and install it on your computer, create a new one, or upload your company IT approved certificate and thus remove the warning.
I am not sure what you mean about the ‘handshake problem’. A screenshot of that would be helpful.
Edit. You mention the error only happens in ‘the app’. What app? I was assuming you meant your web browser, but perhaps not.
We really need a little more to go on here… Are you using Node-RED? What data are you trying to transfer? Are you using groov View?