I just discovered that I cannot load an FBX model in Monogame which uses textures in the form of png images smaller than 4x4 pixels. I occasionally use 1x1 pixel textures to add solid colors to my models, so this threw me off a bit. Easy enough to work around, but still seems like a bug. The error I received was simply "HRESULT: [0x80070057], Module: [General], ApiCode: [E_INVALIDARG/Invalid Arguments], Message: The parameter is incorrect.". Increasing the texture size to 4x4 pixels resolved the error.