Need help. My Switch Lite keeps failing to connect to voice chat in a game:

Can't connect to the server.
The server may be busy, or your network connection
may have been lost. Try again later.
Connection test: Internet Failed
The connection test passes sometimes and fails other times. Im on home Wi-Fi. Ive restarted the router and the console. Is there a setting Im missing, or is this a known issue?
Ive seen ppl mention NAT types and router settings, but i dont really know where to start. A simple checklist would be amazing.
I'm happy to try settings changes and report back. I just want to be able to play online again without restarting everything every time.
