Hi Timothy,
You seem to reset your device or re-install Media Burner. The data of in-app purchase has lost. So the app asks you to pay again, but you don't need to. 
A restore button will be provided, you can restore your previous purchases. It's coming soon, please wait.

Hi Omar,
I really want to help you, but I need more details, can you take a screenshot of the error and post here?

Update to latest version

Sorry, Apple doesn't provide any related API to import muisc into music library other than via itunes on computer

A Restore button will be provided, you can click it to restore your ever purchased items to remove all of ads. Please wait, it's coming soon.

A restore button will be provided, you can remove all ads with it. Please wait.

A restore button will be provided soon, please wait

It's coming soon, please wait.

You delete all of your music? Or all of the music just disappear and you do nothing?