I got a new android device but unable to purchase VirtualHere license

Hi.

I've been using VirtualHere on an android tablet for about 2 years.

And recently, I got a brand new android tablet.

Obviously, VirtualHere says "This Sever is unlicensed, some features are unavailable."

But I can't figure out how to change the registration key.

If I select "BUY LICENSE" on the pop-up menu, it directly connect to Google Store and it says: 

"You already have this item." 

I think it's because I previously bought a license through Google Store.

What should I do with this? 

Is there any way to license this server?