Uninstalling is not the same as deactivating. You're allowed two activated installations, but it sounds like something has made PSE think it's installed on more than two computers. To fix this, go here:
and you can usually start a chat session and get it straightened out right away.
Launch the Editor on the machine you don't want.
Click Help >> Deactivate
You may need to re-install again and then deactivate or seek help from support as suggested by Barbara.
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