Hi Andrew,
Thank you for the details, I’ve logged in to check your configuration.
Unfortunately I have no idea yet, why the products are not displaying. At first I was suspecting that there was something wrong with the configuration, but it’s clearly not the case here. I’ve even created a new search instance to double check this with the default configuration, but that’s not working either. There were no similar issues reported recently, so this is something new.
I suspect that this is either some kind of conflict, or an unkonwn bug, or maybe a plugin file corruption. Can you please also add temporary FTP access? I would like to do a step-by-step debugging of the search code, to see what’s wrong with the query, or why the products disappear from the results.