is there any way for you to enter the recovery mode? Do you get there when you hold Vol up and power button at the same time (you should get to a screen with the android logo and the message “no command”, if you are there press power button and shortly Vol up again)? For me that sounds like a software issue. Is the booloader unlocked?
Adb only works if your phone is on and adb enabled (or with TWRP recovery). When your phone is in fastboot mode, you can work with fastboot commands. If your bootloader is locked though your options are limited.
I can’t obtain android logo, phone never pass the “fairphone” logo. I tried VolUp + Power, and then releasing power, the other way, releasing VolUp. I tried your sequence without any better answer than fairphone logo.
Bootloader is not unlocked since I did nothing with it.
I really can’t understand how ppor designed those so-called smart-phones are : If my computer has a software problem, I format everything. With phones you can’t do such things