M1 Pro only allowing 2 extended displays, not 3

While working at my previous job, I had an M1 Pro 16" MacBook with 3 external displays - all 27" iMac style displays with adapters that converted thunderbolt to usb-c.

Now that I was called back to work (they let me keep the displays), I got another M1 Pro and now only 2 at a time will work - first one fine, 2nd one fine, 3rd one blank. remove 1st or 2nd and now the 3rd one works with the other that was left in.

In the time between original job and being called back, I purchased my own 16" mbp M1 Max. I tried it as well and same thing - only 2 were supported, third one blank and if removed either of the first two, the third one came on just fine.

Any ideas why, if I remember correctly, why only 2 extended displays max seem to be supported?