I just joined a company with unlimited PTO. Last week I found out one of my direct reports took less than one vacation week last year. I told the team they had

I just joined a company with unlimited PTO. Last week I found out one of my direct reports took less than one vacation week last year. I told the team they had to spend all vacation within the year (22 days). We're all spread in Europe. Not taking vacation could be a liability for the company, not to mention that tired and stressed people makes a lot of mistakes and I cannot afford loosing any engineer due to burnouts.