MacBook Pro M2 suddenly won’t support 2 external monitors anymore

what changed yesterday?

did you do any software updates?

are you using Docking station that features DisplayLink software?

M-series with PRO processor supports up to Two fully hardware-accelerated External displays. (three for Mac mini)

The Mac does not rely on Windows-like side-loaded "Drivers" which are actually packages of resolutions and settings for a specific display. Instead, it goes straight to the immutable source -- it asks the display itself.

To get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. "No signal detected" is generated by the DISPLAY, not by the Mac.

This query is only sent at certain times:

• at startup

• at wake from sleep — so momentarily sleeping and waking your Mac may work

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• hold the Option key while you click on the (Detect Display) button that will appear in Displays preferences (from another display)

so try doing some of those things and see if the display comes alive.

Re: “when I connect the third, the second one stops working”

A MacBook Pro with a M2 Pro chip supports up to two external monitors. It does not support three. If you are connecting three, it is no surprise that you cannot get all of them to work.