So is it getting exactly 60? No more,no less? Does it fluctuate? Have you tried the built in monitor?
If it's absolutely locked on 60, zero fluctuations, there may be an issue with afterburner reporting wrong.
I know you said you had no other games installed,but now would be the time to do so. Just to see if this problem is specific to cod or not. There's free games you can download on steam and epic currently if you don't want to spend money. I think even gta5 is free right now on epic.
It's worth a shot. If cod is the only game showing this behavior it could very well be a cod issue. Or a monitoring app issue.
If other games are locked at 60 then you need to deep dive into any possible locks you may have and not know about.