Failed to find a solution. System matrix is zero. Returned solution is not converged.

I am trying to solve 2 coupled ODEs and am using the coefficient form PDE module to solve it. I have zeroed out the coefficients of the terms with time derivative. Btw this is a 1D problem where the variables are only a function of x. I get the error

Failed to find a solution. System matrix is zero. Returned solution is not converged.

After going through the comsol discussion forum I found that it must be a case of BCs. I have 4 boundary conditions for the problem: 3 drichlet boundary conditions and 1 constraint. The constraint contains derivatives of the 2 variables. Is this the problem.

And after some more runs the error changes and I get

Failed to find a solution.
Singular matrix.
There are 28 void equations (empty rows in matrix) for the variable mod1.omg.
at coordinates: (0.4), (0.433333), (0.466667), (0.5), (0.533333), ...
There are 28 void equations (empty rows in matrix) for the variable mod1.u.
at coordinates: (0.4), (0.433333), (0.466667), (0.5), (0.533333), ...
and similarly for the degrees of freedom (empty columns in matrix).
Returned solution is not converged.

There is also a warning :
New constraint force nodes detected: These are not stored.