Clearly I’m doing something wrong. Guidance please

I let my daughter create her own sleep schedule. That has become her routine now.

So, the issue is that the past few days we’ve been out and she’s been tired cranky, so I come home quickly so she can nap or go to bed. But then I end up sitting there for 60-90 minutes trying to put her to sleep. I’m confused. She was so tired when we were out- so why wont she go to sleep easily when we get home? This has happened at both bedtime and nap time.