If you hear the front fan working then this could be a blend door actuator or the tubing for the heating/ac fell apart behind the dash. Hands-on inspection is needed.
Use this link to find a good shop near you.
Alex
https://repairpal.com/repair-shops
RepairPal Certified shops can diagnose and repair your 2015 Dodge Grand Caravan. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.