Ctrl C and Ctrl V not working

I'm glad it's resolved, or at least appears to be.

I used to teach diagnostic thinking to scientists and engineers. One of the first step when you encounter a deviation from the norm is to get a complete description of what's happening, where it's happening, when it's happening AND, significantly, where it's NOT happening but might, when it's NOT happening but might.
In your case, that's why my first question was whether it was happening in Word/Power Point. That list could have included other software you might be running.
Because as soon as it's clear that those keyboard shortcuts are not working in any of the Office suite of products, it becomes clear that it's not an "Excel problem" but that the cause has to be located elsewhere in the system.
Finding a cause is potentially a lot more complicated than that.....I've had instances where a device goes haywire after a period of time, say three hours; works fine until then.... or a TV that scrambles the image on some channels but not others....
The goal at the start of Diagnostic Thinking is to describe the symptoms as thoroughly as you can so as to eliminate possible causes (hypotheses) that don't fit the symptoms. In this case, once you know the problem manifests itself outside of Excel, you've raises serious questions as to whether Excel could be the cause.
All to say, next time you experience some deviation from expectations, do some quick tests with comparable programs or situations to see where the boundaries are between what's happening and what isn't.