Getting audio to studio monitors in Garageband

I'm using a MOTU 828mk3 and a pair of Yamaha HS-80Ms. As far as I'm concerned, everything is connected properly. My main outs are running to the monitors, and the main out selection in the MOTU's audio preferences is set to Main Outs. If I run a guitar cable to the Mono 1 XLR/instrument input on my MOTU, I make sure to turn the mutes off on both mix 1 and the mono 1 input. After that, I make sure monitoring is turned on for mix 1. Once I see that the MOTU is receiving input on its meters, I then change both the input and output sound preferences for my system to MOTU828mk3. After opening Garageband, I set its input and output sound preferences to MOTU828mk3, create a new instrument track, select MOTU Mono 1 in the track information panel, turn monitoring on in Garageband, and record-enable the track. While recording, I am able to receive the audio input, however, when attempting to play it back, nothing is coming through the monitors. Much appreciation to someone who can help me solve this problem.