Network computers losing search index. (Windows)

I’ve been doing some computer work for a local business, and have successfully fixed most of their issues. They recently upgraded two of their workstations to Windows 10, while their primary office computer is Windows 7. They’ve been using shared folders to be able to look at work orders from the other computers, which I had to set back up on the new Windows 10 computers. Had to do some tweaking with Norton so that the computers would play nice with each other, as they didn’t want to communicate at first.

I’m not overly family with Norton or its settings so it took a little trial and error to get the shared folders and printers working on the new Windows 10 computers, but eventually had them working smoothly. The next time I worked for them however they let me know that they were unable to search the shared folders from the two windows 10 machines. Even searching for terms they can clearly see in the names of files in those folders says there are no results. I reindexed the folder from the windows 7 machine that is acting as the server, and looked online to check settings that had to be changed on each machine to make searching work. Before I left everything was working fine.

Went back today for the same problem, not searching. I had found another setting in Norton through some research which I thought could have been the culprit, and gave full access to the network they were on, and searching started working again. However not half an hour after I left his store I got a call that they couldn’t search again. Luckily his folders are still being shared (that had stopped at one point before I tweaked Norton).

He is contemplating buying a license for Windows 10 for their server machine, something I see as helping a bit just having his whole network on the same OS, but also don’t want to advise him to invest in something that may not fix the issue he is having. I was leaning towards Norton being the problem, but despite changing all the settings that seem to be related the problem keeps coming back. The shared folders keep losing indexing (or something along those lines) with the server computer.

Any suggestions would be greatly appreciated!