Is your tablet rooted? If so, it sounds like you have the wrong recovery image installed. I have a rooted SM-T325 with TWRP 2.7.0.1, and I get that same message. However, a few seconds later my tablet loads the Team Win splash screen and boots into the TWRP menu.
I would try flashing the stock recovery image for the T525, and see if it fixes the problem.
