PBP does not start from postmarket OS image burnt to sd card

[mikehenson]

Do you have an idea what I could do? Thanks again!!

I think you need to get Tow-Boot on the SPI.

I am not sure pine64 uses the wiki anymore, I think they moved everything to "documentation"

From the RK3399_boot_sequence

1. loading from NOR flash on SPI1
   
2. loading from NAND flash on SPI1
   
3. loading from eMMC
   
4. loading from SD on the SDMMC controller
   
5. bringing up the OTG0 USB controller in device mode and accepting control transfers to load programs
   

The eMMC may have an issue booting. You may need to Disable the eMMC so you can boot off the SD. Once booted off the SD, I personnally would try to get Tow-Boot on the SPI.