Hold power, vol up, and vol down. Try that, if that does not work try holding the power button down till the phone shuts off, they hold power button and vol down this should get you into recovery.
Power button + vol down is the button combo for
bootloader, not recovery. Bootloader and recovery completely different things, so its important not the confuse them.
Power + vol up will restart the phone (similar to a battery pull on phones with a use accessible battery).
Power+ vol up and vol down is not any button combination for this phone I am familiar with.
Its not clear whether the OP is having trouble accessing bootloader; or if he can access bootloader but not recovery. Again, these are 2 very different issues. You are right, in that failure to access bootloader is almost always a matter of user error in not performing the button combo correctly. If the phone is stuck on the boot splash (which is what it sounds like) the correct sequence would be:
1) Hold power + vol up until the phone reboots.
2) The
moment the screen goes black, but
before the boot splash screen, let go of the vol up, and press vol down
3)
Do not let go of vol down until the bootloader screen appears
Failure to get into bootloader is usually because either the user started pressing vol down to late; or let go of it too early. As long as the screen comes on, bootloader is virtually always accessible.
---------- Post added at 12:20 PM ---------- Previous post was at 12:08 PM ----------
So I was on my TWRP recovery and I wiped Dalvik cache and all the other things that I was able to wipe while I was on the TWRP recovery and now my phone won't boot up. It is stuck on the white screen that says, "htc powered by android"
I assume that I probably wiped the os and everything.
Of course the phone won't boot. If you wiped /system, the OS is wiped.
If you don't know what it is, you shouldn't be wiping it.
Some folks like to wipe /system before they flash a new ROM for the sake of being thorough, but technically this is not necessary. Flashing a ROM always wipes /system.
But it doesn't sound like you were flashing a ROM. What were you trying to do, and why were you wiping things?
My advice would be to access bootloader as described above, then select recovery. Alternately, use adb to reboot into recovery:
adb reboot recovery
If you still can't get into recovery with either the adb command or from bootloader, its likely that recovery was somehow damaged or otherwise not accessible. Use fastboot to flash it again (boot into bootloader, select fastboot mode):
fastboot erase cache
fastboot flash recovery "filename.img"
(where "filename.img" is the actual name of the desired the recovery file with no quotes, placed in your fastboot folder on your computer)
Once recovery is working again, either restore your nandroid or flash the stock rooted or custom ROM of your choice.