Environment: (Settings you have changed (e.g. Auto Download). “Unusual” devices you use (e.g. Bluetooth headphones). Did you select another media player?)
Since cell data won’t be used while connected to Wi-Fi, I would suspect that something changed in your local network environment, which could include a VPN or the Wi-Fi network you typically connect to. The easiest way to check is to go to another place where you typically connect via Wi-Fi and see if downloads work.