Hello,
have KVM version, but when I add my 4th PC to the grid, it removes one that is already set up.
I dont show that you have any version of MP under your sn*********@gmail.com account - no products at all under it.
It would be a 3rd, not a 4th, that it would be removing if you had KM (2 PCs, the Primary and 1 secondary).
You can go to the 'About' menu in the MP config and it should say what version you are on. If you are on KM, use the 'Change License' button to change to it:

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Sean Drohan
Stardock Customer Service Manager