Calculate the inverse of a matrix with many variables?

Hello, all. I am going to find the inverse of the matrix after the derivatives. But, the system terminates the calculation during the process. For the code, please see the attached file. (I think it is invertible because I tried to consider the similar matrix with fewer variables. It works, but it is not working for more variables. ) So, what is the problem inside? (My initial guess is that the memory is not enough. So, I tried to move the calculation to the Wolfram cloud student online version, but it is still in vain. ) How can I fix it? Many thanks!

InverseOfMatrix.nb (7.02 KB)

Your file is missing a definition of F.

Yes, I tried to leave it undetermined to find the general form so that I can determine later on. So, is it the main reason to harm the calculation?