Q: My new iMac came with a wireless keyboard that only allows me sign in at startup, but afterwards it won't type a single letter, the caps lock key doesn't turn on the green indicator light either. Any idea why?

Thanks for your response BDAqua, I'm using my other laptop to reply. Your suggestion tried, but didn't work. Strangely, the keyboard stopped functioning after the new iMac is setup with ID and password... then it refuses to type a single word.

I switched to guest user, and you know what, I can type and everything. I must have touched a key or checked certain options during the setup.

I'll try your suggestion and let you know.

Problem found,

System Preferences>

Accessibility>

Select Keyboard (under title "Interacting") >

uncheck both Enable Sticky Key and Slow Key

Now I can type.

Thanks.