nRF52840 (ISP1807) not resetting during powerup

[Axbaldwin]

I'm having some issues with a design I'm developing using the ISP1807 bluetooth SOC (contains nRF52840). Every time I apply power to my device I have to manually reset the MCU by shorting nRESET to ground. I tried adding a POR IC (TPS3831) that holds nRESET low for 200ms after power reaches 3.3V but this did not result in the device resetting either, and I still had to manually reset it by shorting the pin to GND. Do I just need to hold nRESET to GND longer during startup? Or do I need some circuit solution that lets the pin go high, then pulls it to GND for a few ms before letting it go high again? Or is there another better solution out there that I haven't thought of?

[Kenneth]

Have anyone at Nordic reviewed your schematic and layout? Do you see this also when using the nRF52840-DK?

Have you tried adding some debugging (e.g. UART) to check if the problem may be related to an assert?

Are you sure you are doing a complete power cycle, and that there are no residue voltage on the board that may be feeding the nRF52840 through a GPIO?