No power to keyboard
Have a friend that has an older keyboard that takes batteries. Its clean but no power. He has done everything to try to resolve but no green light at all.
iMac 27″, macOS 12.7
I suggest starting by taking a look at this article to see if it can help:
One thing that stands out from this article is the type of replacement batteries that are being used. They should NOT be the rechargeable type.
No green light could indicate that, even with the proper batteries, that either power is not getting to the keyboard's logic board, or that the status light is faulty. The latter would still mean the keyboard should be useable.
You mention that the keyboard is "clean." Did you closely inspect the battery compartment to make sure that there is no corrosion on the battery contact points.