....to get stair carpeting to stay on the tackstrip is to have the carpet installed by a pro.
No offense, Robert, but this is not an area to be carpeting yourself without the proper knowledge & tools. Flat on the floor is one thing; stairs are another; carpeting improperly installed on stairs is an invitation to injuries or lawsuits.
The carpet needs to be stretched onto the tackstrip, requiring a knee-kicker. I'd not advise you trying to learn to use one of these on a stairway, either; it's easy to cause permanent knee injury attempting to use one without guidance.
If you're installing carpet on your stairs with tackstrip & pad, it's got to be stretched, and stretched properly, to not be a danger. Please have this done by someone with experience.