"Error contacting licensing server"

First of all, check your Internet connection.
If your connection is good, please reinstall the app using this instruction:
1) Delete app and log out from all of your Google Play accounts on your device.
2) Go to settings-> Applications-> Google Play Market and make "clear data"
3) Next open Google Play Market and login with the same Google Play account that was used for the original purchase and install Tabs app. All your in-apps that you purchased previously will be restored. If you still can't restore, please send us full receipt of purchase and your Ultimate Guitar account’s username (if you don't have an account, please register one and login into the app). 

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