Live notifications and emails have stopped for all new content that has been posted. We still get the moderation queue notifications but not the ones for forums or blogs.
how can We restart/ purge this service so it can work again?
Can you confirm that
All three of these can be confirmed by navigating to Administration > Site > Message Buses > Socket Message Bus (or whichever is connected) > and then Diagnostics:
You should see something like the following. Note the inclusion of the Job Server alongside the Web nodes.