Sometimes glue which has come unstuck can be restuck with an iron. I just place a few sheets of packing paper between the sole of the iron and the loose veneer. The heat from the iron remelts the glue.
If that doesn't get it done, you might try a 5-minute epoxy spread thin, and a roller to continuously press down the loose veneer until the epoxy sets.
If that doesn't get it done, you might try a 5-minute epoxy spread thin, and a roller to continuously press down the loose veneer until the epoxy sets.