Solving system of 3 differential equations in a solve block

At least one of the problems in your sheet lies with the definition of Mh2(x).

In there you probably wanted to multyply Ay with (x-a), but you entered it as the function Ay with (x-a) as its argument. The same goes for p1 and (x-a). You must explicitly enter the multiplication operator in both cases.

Like this:

Another problem lies with the fact that you constrain v(a) to be equal to 0, and a little further you constrain it to be equal to v2(a). I should expect that's the problem that is flagged, as shown in your picture.

Success!
Luc