I'm getting an error that I can't figure out at all. I'm trying to invert a 4x4 matrix. All of the terms in the matrix are 3x3 matrices except for the m's are constants; hence, a 12x12 matrix.
It seems like the problem might stem from nesting the matrices and then trying to take the invese as if a 12x12 matrix. I've upload my sheet. Culprit is on the bottom of the 3rd page.
Also, a simpler version illustraiting the point is attached.
Sorry. I should have read your original post more carefully. I got distracted by the weird error message
You have a nested matrix. That does not translate into a larger matrix. It is exactly what it appears to be, a matrix of matrices, and you cannot invert that.