I have no trouble booting to fastboot: I simply press power + vol. up simultaneously and that’s it.
However, I always have trouble booting to custom recovery, in my case, TWRP. For my model (asus X00PD) I should press power + vol. down and then release, however, I don’t know when I have to release or if I have to press power and a bit later the vol. down button, nor do I know if the device only boots to this mode when the usb cable is not plugged in.
advice welcome
Have you tried pressing both simultaneously from off until the asus logo appears?
And then let go of power, continuing to hold volume… Maybe
You need to read a step by guide and follow the steps.
YouTube a few vids and just follow along. That should answer most of your questions
Assuming your phone is rooted, just install “super reboot” from they play store, that gives you the option to boot from your OS directly into recovery.
