my bluetooth suddenly stopped working on imac. wireless keyboard and mouse don't work

Hi rooney12,

Welcome to the Apple Community.

I guess you checked the batteries in your keyboard and mouse are ok ?

Apple support have articles online that may help troubleshoot:

If you can't connect your Magic Keyboard, Magic Mouse, or Magic Trackpad to your Mac

https://support.apple.com/en-us/HT204621

Resolve Wi-Fi and bluetooth issues caused by wireless interference

https://support.apple.com/en-au/HT201542

And

If you need more help:

you may need to add the iMac's model (ie: year of Manufacture), to this discussion

and

the Mac OS version that is installed.

( These details can be obtained by clicking the Apple logo on the left in the top menu bar > About this Mac)

Also, if needed:

If you have a wired keyboard and wired mouse handy, you might be able to make of use them. at the least, temporarily .

All the best :-)

The following will require any USB keyboard and mouse. If you don’t have them, borrow or buy them, they are inexpensive!

1.     Connect the USB keyboard and mouse to the computer.

2.     Open System Preferences – Bluetooth

3.     Un-pair the wireless keyboard and mouse.

4.     Turn off Bluetooth

5.     Restart the computer in Safe Mode per the directions in https://support.apple.com/en-us/HT201262

6.     Restart the computer normally.

7.     Open System Preferences – Bluetooth

8.     Turn on Bluetooth

9.     Re-Pair the wireless keyboard and mouse.

10.  Unplug the USB keyboard and mouse and begin testing the wireless devices again.