Alcatel Pixi 4 Hardware Button Issues following Screen Replacement

I finally received a part for an Alcatel Pixi 4 (4060S). I removed the broken glass using a heat gun, and that went fine.

However, before removing the glue cover-thing on the new glass and installing, I put it in place and tested the buttons.

Only the recent-apps hardware button works when the glass is in. All three hardware buttons function when touched with a finger when the glass is off.

What may be causing this? I tried removing any glue residue from the OEM screen off of the sensors, but that didn't improve the situation.

Does anyone have any experience with this type of issue?

What resolved it for your device?