Can a man lose his ability to make babies with old age?

No! If you can can get it up, you can get her pregnant (assuming your woman is still fertile as well)

The only reason you couldn't is if you were in an accident and can't have babies, OR if you have an unhealthy lifestyle then your sperm wouldn't be unhealthy (drinking, smoking, drugging, promiscuity) . But for men it doesn't matter how old they are. There's not timeline. If you're healthy you can conceive.

If you and your woman want babies but she can't get pregnant, then you can either do in vitro with a egg donor, or adopt. But only if you want to.