When I go to build one of my test designs I get this error, anyone know possible causes?

Sounds like you're dealing with a small design. If that's the case, check this: https://github.com/efabless/openlane/wiki#how-to-add-a-small-design

That makes sense, thanks

Did your placement run successfully? I was getting the same error when I tried to gen_pdn without correct placement.

yea I got it to work