Can't boot into twrp on DP4

hello I'm trying to make a nadroid backup before updating to dp5 but Everytime I try to enter twrp it won't boot past the twrp splash screen.. how can I fix this? It's worked before for me on dp4 and I didn't do anything that would cause this that I know of.

Does anyone have any suggestions? Thanks.

Sent from my Nexus 6P using XDA-Developers mobile app