I recently bought a RPI 4B + eMMC + penta hat module.
Flashed the ubuntu focal image onto the eMMC, booted the device and then followed the Penta HAT SW install procedures listed at the wiki.
However, when I try to power on the device with the HAT plugged in (with no HDs attached to it), it does not boot. A static green led lights up on both RPI and HAT, but the small blueish activity led never comes up and the HDMI signal is never activated.
If I unplug the HAT, the RPI comes back to life again. Am I missing something here ?