Cannot boot into ROM?

[Pavlovthedog]

Hi all. I am trying to install a custom rom onto my pixel xl, but everytime I sideload, or just install straight from twrp and try to boot up, I get the error, I just go to the "your device cannot be checked for corruption" screen. Anyone know what I'm doing wrong? Thanks.

 

[bcrichster]

Is this while booted into TWRP recovery?

 

[doniago]

Are you referring to the message you'll always receive if you've unlocked your bootloader, which you'd need to do in order to root? If so, the message goes away after a few seconds. A screenshot might be helpful.