Foundation no longer acts like a foundation.. Help??

I have been working on this MOD and I have a Basic Thatch Foundation Variant, and it will not let me place a wall on the foundation. I have another triangular foundation which was based on the first one and it works just fine. I have gone through and checked all the settings and they look the same between the two foundations and yet the first foundation will NOT let me build on it. It just keeps saying that it requires a foundation to build on. The second foundation works just fine.
Is there some obscure not very well identified check box that could cause this?
I am losing too much hair to keep poking at this on my own so throwing it out to the community for assistance.

Hey man, I just did a foundations mod – I’m sure we can figure this out. I’ll load up my devkit tonight and we can go over all the settings/checkboxes you’ll need.

And you should check out the Discord channel if you haven’t already. I’m on there as “RedDwarf”. Here’s a link that can get you started: