Hi there, swandy!
Thanks for visiting the Apple Support Communities. After reading your post, we understand you have a SteelSeries Nimbus+ game controller that is not working as expected with your Mac. You've come to the right place to get some help!
If the issue occurs in multiple games, we suggests reviewing the compatible devices to confirm the controller is compatible with your iMac model: SteelSeries Nimbus+ Wireless Gaming Controller - Apple.
Then, check out the "If your controller doesn't connect or work as expected" section of Connect a wireless game controller to your Apple device - Apple Support.
If your controller is still not working as expected, check out the troubleshooting SteelSeries has for the Nimbus+: My Nimbus+ is not responding – Support. If you still need help after that, click on the "Contact Us" link in the upper right corner of the SteelSeries page linked above. It should open a contact interface for you.
If the issue is specific to the app, check for any in-app controller settings that you might be able to adjust. Then, try the steps outlined in the Apple Support article If an app freezes or quits unexpectedly on Mac - Apple Support. Then, reach out to the app developer if you have more concerns: How to contact an app developer - Apple Support.
Cheers!
