Default Stuck in Samsung Galaxy S4 splash screen

Hey all, in need of a little assistance. I was running the tri-force 5.3 rom. loved it, but saw that 5.4 came out. I tried downloading it and got stuck at a screen where it said it had failed. i then tried to follow the steps by reflashing the stock rom and now i am stuck at the spash screen with the red and yellow words at the top. or it pops up saying System software not authorized by samsung has been found on your phone. with yellow triangle in the middle. Anyone know what i need to get past this screen? I believe i was running an MDL prior to this if it helps. I also can still get into the download screen (power + vol down)