Could you go into NVDA's Tools menu, and under Remote, make sure that 'Mute Remote' is not checked in that submenu?

Assuming this is unchecked, could you try NVDA+S on the remote machine to make sure the 'speech mode' is turned on, on 'talk' rather than 'off'?

If all this doesn't solve the issue, the only thing I know you can do is, if possible, restart NVDA and the machine remotely and it should come back up again as expected. If you had a connection issue, then it would have meant that the remote server you're using and/or the computer being controlled was off, or NVDA on that machine was off, but this probably isn't the case here.

Hopefully this helps!

Kind regards,