New version problem

I have a 2 year license

When I updated to the latest version, I was told it is expired but I could return to the newest available version.

However, after I installed that version, it popped up an error:
"For security reasons, updates that downgrade version of the application are not allowed. Refusing to downgrade app from version 1639 to 1596. Aborting update."

It's stuck between the latest version and downgraded version. So I can't use BetterTouchTool anymore, even I had 2year license.

My Mac mini is 2011, version 10.13.6

Help me please!

Nobody helps me?