my iMac says it cannot connect to the keyboard, how can i fix this?

Hello chloefrombronx,

Thanks for using the Apple Support Communities!

I understand that your keyboard is not connecting to your Mac as expected. Is this a USB keyboard or a wireless keyboard?

From your question, it does sound like your Bluetooth keyboard isn’t connecting, so I would begin troubleshooting by reading over and working through the suggested steps from the following article.

If your Apple wireless mouse, keyboard, or trackpad aren't working as expected - Apple Support

Cheers!