ramps1.4 and new firmware rc7

hi , i just try to test the new marlin firmware and i end up screw two arduino board with two sets of ramps and driver. since i tested , i see the 3 axis blink with this ?, as you can see the image . i try to go back to old version of marlin and same think now on both board mega2560/ramps1.4 before the update all ok, now i can get to stop blinking. i can move axis with no problem end stop works. ??? any idea. i try to go back on the arduino ide software to old version nothing.

The blinking axis names with a ?, mean that they haven't been homed.

Thank you , I never hit home, got panic when I saw blinking letter. I burn a mega 2560 arduino once.
Thank you .