Some help with 'Could not read system exclude file' for a confused layman

Expected behaviour

A lovely long list of healthy files and folders when I open the OwnCloud folder via the client.

Actual behaviour

Cannot open the folder anymore. There’s a red cross in my little cloud icon and the error message above.

Client configuration

Client version: 10

Operating system: Windows 10

OS language: Windows

Installation path of client:

Sorry for the dearth of information. I installed OwnCloud a long time ago at the prompting of the company but we run a skeleton staff (not for profit) and as unlikely as it seems there’s no-one but me to sort this out. It was working fine, now it isn’t, it’s on a dedicated server with ANS and I’d love it to start working as it used to. I have kept it up to date.

All help sincerely welcomed, but should be pitched at ‘eager noob’ level …