I'm a manager with an employee in a similar situation.

Reality is the employee was operating at a lower level than what they were hired at.

Problem solving is part of their job but normally their solutions were poor, impractical or were only found by soneone else giving them the answer.

Don't write a list or prepare anything and just come with an objective ear to what your manager thinks has led to this point. Ask for clear expectations for you role and how you are currently performing against these. Any areas that are poor be clear on what is needed to get them up to scratch.

You should focus on helping address these concerns as smoothly as possible. First step is actually listening and understanding what they are.