CLBDG Please try the suggestions in the first few replies to this master thread:
400 - Bad Request | EA Forums - 13121426
Even though the error is different, the replies contain all the usual troubleshooting suggestions for issues with the launcher connecting.
If none of that helps, can you try a different connection? If your computer has wifi, you could set your phone as a mobile hotspot (using data, not your home network) and connect to that instead. The idea is to find out whether the problem is coming from the computer or the network or its equipment.