White line running across iPad after repair

Did Apple, or an Authorized Apple Service Provider do the repair? If so, then return to the provider for them to take care of it. If you had a 3rd party do this repair, then see if they will provide you service. Apple will no longer service a device that has been repaired by a 3rd party.

You're welcome. unfortunately, at this point you with either try to get this 3rd party to honor their repair, or you will need to replace the iPad. Good luck.