Mac studio not detecting display

Swapping cables around is a hedge against a cable that is broken. It does not help if your cable does not meet the requirements to run your display at your desired resolution, completely error-free.

Having the connection be flaky does indeed suggest that your cables may not be adequate, because what shuts down the display connection is if it generates errors in transmission. A cable that is pretty good, but not quite good enough, can do exactly that.

What resolution display, and what cables are you using to connect it, and how long is that cable?

Well, it actually is possible that it's the cable; if the cable is below spec (as many cables are despite their claims), it might allow the display to be detected sometimes but not others. If you have or can borrow another cable, preferably of a different brand, it would be worth trying, at least. It also can depend on cable length; the cable for a high-end display should be less than 3 meters.

There's some additional discussion on the issue, with some other things to possibly try, in this Community thread:

All 4 external displays on Mac Studio ran… - Apple Community

Regards.

Cables that are of iffy spec can have all sorts of unintended consequences. But if you've tried other cables that are of an appropriate length and which have come from reliable vendors (and off-brand cables that might have some from some unknown Chinese vendor from Amazon are not reliable vendors), then the cable would seem not to be the issue.

There are some other suggestions in the thread I linked to. Perhaps something there will help. The only other thing I can think of to suggest would be to swap the current fourth monitor with one of the others and see if the problem persists with that fourth display or moves with the specific monitor. That would provide some additional clues.

Regards.