I use a number of keybinds with the Alt key as the modifier and they have been working fine until today. The alt key definitely works outside of the game (can alt tab etc.) and Alt+Z still works to hide the interface, but otherwise any keybind with the Alt modifier is ignored (can’t rebind anything to alt+number and existing binds don’t register). Any idea how to fix this?
EDIT: issue is happening on Classic, not sure if the same true for Retail
Hey Pomegranated
Assuming your Hotkeys are still set up properly, this generally happens if something else is set up to use those hotkeys, like overlay software for example, and it’s stealing the inputs entirely
What you can do to narrow down the cause is to close background applications and start things up a couple at a time until you narrow down what exactly is causing it
Hm, it’s suddenly working again today. Very odd considering I haven’t installed any new applications recently. Thanks for the reply, I’ll try it if the issue comes up again.
How did you fix this? I’m getting the same issue today. Alt+number keybinds aren’t working, but alt+letter ones are.
I have also just noticed the same issue. I closed background applications, and the problem persists.
For me closing Photoshop did it, good luck figuring out what is doing that for you.
This was a great find, If i load wow before photoshop, there is no problem, but if i load wow after photoshop it is a hit and a miss to wither the Alt key works or not.
So a quick reload on photoshop works a treat.
Same for Illustrator. Thanks a lot for the great finding, Druidane.
Hey! Thank you so much for your hints! For me it was Nvidia Experience overlay (alt + y ingame to trigger) which had binded alt + r to “toggle performance overlay” 
when deleted it works in wow
for me it was also Nvidia Experience. go to Nvidia Experience and turn off IN-GAME OVERLAY.
Thanks for the updates and resolutions everyone, but as this is a very old thread I’m now closing it.