I would assess and uncover why the contacts are inactive. Did their role or responsibilities change? Are they still with the company? Or does this signal a larger issue within the account that may indicate churn risk?
Abigail Benson what did members agree to when they joined your CAB? Do you have term limits? How many total members do you have? Is it feasible to speak personally with all your inactive members? Get some status on them from your CSMs?