Hi there.
We have recently migrated from SDK 2.6 to SDK 3.0.
We have a custom-made external board, which we used to program with the nRF52840 DK when using SDK 2.6 (for Matter examples like Light_bulb). This involved building the project, flashing it, and after flashing, when we turned the board off and on again, our custom board started advertising.
However, after migrating to SDK 3.0, when we flash the same Light_bulb example or any other Matter sample onto the same board, it does not advertise. It's worth mentioning that when we flash the simple blinky example in SDK 3.0, the LED on the board blinks, indicating that the communication is working fine. The issue seems to be with the advertising functionality for Matter examples in SDK 3.0.
The same examples work fine and advertise on my nRF52840 development kit, but not on our custom board.