I bought BTT ages ago - it works how I'd like to, and my 2-year free upgrades are done. I don't need anything new - I'd just like to continue using the software, as I have been, and as is promised by the licensing agreement. However, as of today, BTT simply refuses to work without me upgrading my license. I have version 2.428 and would like to just keep on using it. The macbook it's on is old too - there's no need for updates or changes. I'd just like access to what I paid for.
Try to restart your machine, sometimes a macOS service used for licensing breaks. A restart usually fixes this.