I was trying to use the built-in intervalometer on the Canon R5 last night, and at first set-up the shutter wasn't being triggered. I played around with settings for a bit, flipped the lens to Manual focus, things like that. Eventually, I remembered that I had changed the behavior of the shutter button half-press to be AEL instead of the default Meter/AF Start. When I changed that back, the shutter was able to trigger during the interval timer.
I feel like I'm missing something in terms of setup so I don't have to remember to flip this setting back and forth, but changing the behavior of the half-shutter press was the only thing that allowed the camera to trigger the shutter (even in manual focus mode). What am I missing? Or do I just have to remember to change this every time?