Problem with 24-70L and 5dii

Hey all, I have a Canon 5dii and 5d classic. My favorite walk around lens is 24-70L. Today when I was shooting images of my niece at the park, my 5dii and the 24-70 stopped communicating. I had to manually focus the lens AND, the aperture display said 00. Weird. So, tonight I put my 50 1.4 on the 5dii, and it worked. So I tested the 24-70 on my classic and they worked together. Sooooo.... any suggestions?

try cleaning the contacts of the lens. Does remounting the lens work?

it mounts onto my old 5d classic and works perfectly. Remounting onto the 5dii changed nothing. I tried a different lens on the markii and it functioned. That is what is so weird. What is the best way to clean the contacts?

I wiped the contacts 24-70l this morning and remounted it on the markii, and it recognized it. Happy for now.

This happened twice to me couple of weeks ago, that the aperture showed 00, i used two different lenses 85L and 24-70L.... I still have no idea what's going.. If this will happen again i will send my camera to canon and have them check it.