Arduino (Adafruit feather m4) to openmv cam using spi problems

I’m trying to get an interface to work between the adafruit feather m4(arduino ide) and my openmv cam. I’ve tried using i2c, but that didn’t work (perhaps because I didn’t use pull-up resistors?) so I switched to trying spi instead. So I’m using the Adafruit Feather m4 as the master and the openmv cam as the slave. I load up each board, switch over to the serial monitor on each and I don’t see anything happening. I’ve put a print inside the “face detection callback” and the “snapshot callback” on the slave side and these routines never get called - no prints. The spi interface I’m using on the openmv cam is using pins p0, p1, p2 and p3(ss). On the “Feather” side I’m using the “standard” MOSI, MISO, CLK and ss is on pin 10. I’ve connect the cs, clk, miso, mosi pins between the devices and I’ve added a ground between them also. I’ve seen posts where people have gotten this inter-board communication working, but they seem to all be using UART. Is this possible using SPI and, if so, what have I done wrong?

The library is designed to work pretty seamlessly with SPI. However, you need to have the RPC slave code running on the OpenMV Cam with the RPC master code running on your Arduino at the same time.