doubt it, it would be a bit more helpful if you were to give us a couple of examples that it fails what you expect, what you get etc. There is also a nice little matrix library at https://paginas.fe.up.pt/~paco/pmwiki/index.php?n=DynMatrix.DynMatrix that you can use for validation.
This is a test matrix:
(3,00, 4,00, 1,00, 3,00)
(2,00, 7,00, 6,00, 4,00)
(3,00, 5,00, 4,00, 8,00)
(6,00, 7,00, 4,00, 9,00)
This is the result of InvertMatrix function:
(-0,14, -0,21, 0,13, 0,38)
(0,22, 0,53, -0,80, -0,41)
(0,03, 0,77, -0,56, -0,68)
(0,03, -0,56, 0,77, 0,32)
This is the result get from many online tools (I have try 3 tools an I get always the same result):
(-0.56, 0.03, -0.68, 0.77)
(0.77, 0.03, 0.32, -0.56)
(-0.80, 0.22, -0.41, 0.53)
(0.13, -0.14, 0.38, -0.21)
As you can see all items value are right but position is wrong:
Right position -> Wrong position
11 -> 42
12 -> 44
13 -> 41
14 -> 43
21 -> 32
22 -> 34
23 -> 31
24 -> 33
31 -> 12
32 -> 14
33 -> 11
34 -> 13
41 -> 22
42 -> 24
43 -> 21
44 -> 23
Note: the determinant is right.