"Could not connect to server" on Switch

It is impossible for me to log into my account on Switch and therefore to play online.
I start up the game and when I select “Log in”, it loads for about a second and then stops. After about 10 tries, it starts giving the error “Could not connect to the server”. If I play offline first and then select online, the same thing happens. I have a stable WiFi connection and all other games work perfectly. I have tried restarting the Software, restarting the Switch, deleting local save data and deleting and redownloading the game and using a different WiFi.

Steps to reproduce:

  1. Open game.
  2. Select “Log in”

Expected Results:
Login screen.
Actual Results:
Loading and cancelling the first few times, then Error: Could not connect to the server.


Game Version:
System Information:
Nintendo Switch on most recent firmware.