Dragonboard 410c: wifi and HDMI output doesn't work after fastboot boot newkernel.img

I’m new for DB410c. I programed my board with a sd card with sd card install package dragonboard-410c-sdcard-installer-sid-893.zip. After program done from sd card, the linux system can start up, and I setup the wifi to our office’s wifi from GUI destop. Here wifi and HDMI display do work.

But I need a kernel whose version is 5.7.7, so I entered fastboot by press S4 button and turn on power. Then I can see a device when I type ‘fastboot devices’, then I type the command ‘fastboot boot boot-db410c.img’, system looks boot up from my kernel version. But I met two problems:

a. HDMI has no output, so I can’t anything on my monitor.
b. wifi doesn’t work.

Anybody can tell me the root cause, or how to check them? Much thanks in advance.

I think you updated the kernel without updating the related modules, and so I assume lsmod output is empty… Have you built the kernel by yourself? You should have a look at part 6. in https://www.96boards.org/documentation/consumer/dragonboard/dragonboard410c/build/kernel.md.html

thank you very much.