Donkey Kong 2600 not compatible?

I was looking at games from the 2600 that seemed to have compatibility problems with the 7800 on the 2600 Connection website. Donkey Kong was not among the list. My problem is that I've encountered several carts that won't work with the 7800 and of them, 3 copies of Donkey Kong.It seems like this is more than just a coincidence, especially since one of the games I tested about 3 years ago and it worked, and when I went to retest it to sell, it wouldn't work. Cartridge almost looks new and is clean. So are there issues with Donkey Kong too? BTW, this is the Coleco version, not Atari.

I put all my non-working carts aside for when I finally get around to hooking back up an original 2600. Then I'll test all of them again and see if they are truly dead.

Phil