Hi binghjs78. My S4 is rooted as well. I downloaded, installed, and opened Ti with no issue. I have not used the root checker app but I would suggest you use Super SU instead.
Once you download and try to open Super SU, it will tell you immediately if your device is rooted properly or not. Once you confirm your device is rooted properly, open Ti. You should be prompted to grant Ti superuser permissions. If this does not work, I would suggest you take MrHost's advice and re-root your device. Here is a screen shot of Super SU in action - Good luck.