Update failed: Download failed. Unauthorized

My (new client’s) wordpress back-end is telling me that an update is available for WooCommerce Custom Payment Gateway Pro, from 2.2.1 to 2.3.1. But the hosting company auto-updates aren’t applying it and when I try to do it manually, I get the message “Update failed. Download failed. Unauthorized”

I’m seeking guidance on what to do about this.

I’m afraid there’s no guidance on what action to take and I can’t find anything relevant on the forums.

WooCommerce is installed at version 5.4.1 and appears to be happy.

There are a couple of other plugins from other sources giving the same or similar messages.