[URGENT] i m unable to go in TWRP recovery mode topic

hii
I install TWRP via odin on my galaxy core i8262. installation was successful and pass shows in odin screen. but when I tried to on my phone in recovery mode by pressing volume down+home+powre key then my phone does not go on any recovery mode neither stock recovery nor TWRP and phone starts. in simple words I m unable to on my phone in any recovery mode.:( so plzz help me... and I have a ques also is my phone warranty is voided by installing custom recovery??:confused: I have only install recovery?? plzz reply soon...:(