Is There A Solution Available

is there a solution available

In that sentence the solution is for Anna, and although there's a problem to solve it's not front and center. This is clear in sentence number 2, where a solution to a problem must be found for the boss (who's paying for the solution to the problem to be found, and expected answers).

there is no solution or there are no solutions

You think: Eh, this person's fine, but I'm sure there's someone better… But in complicated situations, there are not endless options. Instead, there are a fixed number of options — and even if they're all imperfect, you must pick one. That's why you can't evaluate solutions one by one.

Moving forward, it's essential to keep these visual contexts in mind when discussing Is There A Solution Available.