Hi CBIreland,
Thanks for posting in Apple Support Communities! Is your Mac and iPhone connected to the same Wi-Fi network? Check out the tip below from the article Use Keynote Remote to control your Keynote presentation:
If your devices can't stay connected, connect both devices to the same Wi-Fi network on your Mac and on your iPhone or iPad.
If they're connected to the same Wi-Fi network and the behavior continues, ensure that both devices are also running the latest software versions. Outdated software can cause features to misbehave. These articles should help with updating:
Update macOS on Mac
Update your iPhone, iPad, or iPod touch
If you're using Low Power Mode on your iPhone, disable it while using this feature. Low Power Mode can stop certain features from working to preserve battery life.
- Open Settings
- Tap Battery
- Switch Low Power Mode off
Cheers!