Where has my input buton gone?

About 3 weeks ago the input button vanished from all track headers on all of my recording projects. It still exists on the inspector strip on the left side. I have tried reconfiguring the track header multiple times. It increases and decreases the length of the track header bar but no input button appears. I am using Logic Pro X on an imac. I was using an older mac OS so I upgraded to Monterey but that hasn't solved the problem. Any help would be greatly appreciated.