earl_dean, if you haven’t already done so, can you double-check your Manage Buyer Communication settings? Link: https://www.ebay.com.au/cnt/ManageBuyerCommunication

Just in case you haven’t taken a look at those settings lately… and ensured that “Send you messages on eBay while they're shopping” (under What your buyers can do) is enabled with YES. You might even want to try the “turn it off and then on again” for that setting.

If you’ve already gone through that (and I suspect you probably have!), then I’m not sure what else to suggest.