odesolve block: Unable to form a derivative matrix error

Yes, I realized too late that the file was automatically opened in P10. Very annoying and unnecessary that PTC in its greed makes a file format change with every new version.

But you should at least know if the result shown meets your expectations.

It was achieved very quickly, not very elegantly and with a lot of copy&paste by first defining V4 as a function of V3 and then explicitly solving the only remaining differential equation after the derivation of V3.
This dependence of V4 on V3 is probably why Prime has difficulties with this system. Essentially, with your two equations, you are only specifying two different expressions for the difference between the derivatives of V3 and V4. Prime can no longer do anything with this.

Here is a pic of the files content