Firefox Sync asks me to sign into another device

I completed firefox sync, by giving my username, password, and two factor authentication code.

Now, it says inorder to complete the setup, I need to login to another device.

1. I went to browser in another device and logged in. No help.
2. I downloaded into my phone and logged in. The setup did not go through.

I am upset by these choices and behavior these services have taken with this approach. Help me to recover both my loss of emotion by annoyance, and technical help on how to use sync well. Can I avoid the need to login to multiple devices and use the sync?