Postmeta 'views' not updating

I have a plugin in development that retrieves post views from the postmeta.meta_value and postmeta.meta_key fields, but lately WordPress is not updating the number of views. I’ve de-activated all plugins, and still it doesn’t register views. E.g., posts that I know I have viewed recently all say 0 since a couple of days ago.

This worked fine originally, and I haven’t made any updates to my theme or WordPress install recently. Anyone know what might be causing this?