Seems that is takes some time until is finding the SIM. After few minutes I was able to find the SIM.
For more details about this mPCIe modem I downloaded the hardware design and on page 14 there are the pin outs for SIM card and I compared with the schematics from APU6B4 and are matching.
Here is the PDF: https://nextcloud.easynet.dev/index.php/s/8TSRGe9DsK44Dcy
I have this board and I connected in mini PCIe slot 2 the LTE modem SIM7600E-H. https://www.simcom.com/product/SIM7600E-H-PCIE.html
I see the modem in the OS, I can send AT commands, but when I'm inserting a SIM card and try to check the SIM card I got this:Code
Even I have the SIM inserted in the board SIM slot.
I used this modem on another board NF9HB-2930 https://www.jetwayipc.com/product/nf9hb-2930/, and it worked without issue.
What could be the reason that is not detecting the SIM?