Update issues after downgrading using a supposedly expired licence

I purchased a standard licence on the 21st of Jan last year, but after the end of January this year I've been getting a message along the lines of 'Your license was purchased more than two years ago. The standard BeterTouchTool license includes free updates for two years.' I already tried restarting my Mac as well as redownloading the licence file in my email, but I am still unable to use the app.

So I reached out to Andreas about the issue but I am still waiting for a reply.
Eventually I thought to just downgrade to the 'last covered version' which was valid under my licence, and the update seemed to download, except in the last stage, I got a message saying:
'Update Error! The update is improperly signed and could not be validated. Please try again later or contact the app developer.'

Any way I can get the app to work?

Thanks.

you can download previous versions via Index of /releases

Standard licenses receive updates for 2 years, mostly likely you have a free promo license generated via my other app BetterSnapTool, these received updates for 1 year in the past (nowadays 3 months)

Alright thanks!