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We don't you try a contact the Boss division of Roland about this?
They would have better knowledge of this product question/issue than anyone here.
I am a Roland keyboard user and use their apps on my iPads, but have no clue about their Boss line of devices being controlled by apps on an iPad.
I see in the App Store than Roland has the Boss Tone Studio for the Pocket GT
I see no version of the BTS for a GT-1, though.
I suggest you contact Roland Corporation support or search online for the Roland/Boss Website and see if their Website has a support area or contact info.
Best of Luck to You!