There is no TWRP for the xt912. Do you mean safestrap? Which version did you have, which version were you trying to install?
Did you wipe the stock slot?
Sent from my DE Moto X
"She leans into me and I keep my arms around her. I don't fool myself that I hold her together -- She does that on her own -- But holding her keeps me from flying apart."
Moto X DE
Nexus 7 - Grouper
Retired: Droid RAZR HD XT926 Developer Edition / Droid X2