This error occurs when Maple does not find a mathematical solution to a matrix equation representing a system of linear equations.

Sometimes, there is no solution to a given problem, which is a legitimate result.  In this case, there is nothing to fix; this is Maple's response that there is no solution available.

In this example, $\mathrm{Mat}$ has all zero entries while $\mathrm{Vec}$does not. The system $\mathrm{Mat} \. X \= \mathrm{Vec}$ has no solution.