I just turned 60 and have been on testosterone patches for almost a year now. I tried all the test rising supplements and exercise and whatnot and they didn't really do squat. Went to several doctors and one finally diagnosed me with primary testicular failure and prescribed Androderm. Life is a whole lot better now. My advise is to first have blood tests conducted to see where he currently stands. Problem is many of us are "in range" and if so many docs will not prescribe supplemental or replacement testosterone. If your dad is low but in range and the doc won't do anything you either have to find another doc or go off the grid.
Stay safe over there and come back soon.