Not able to download free apps

Fix whatever the problem is with the payment method in your Apple ID account. You need to have a valid payment method registered even for free apps. See the Apple support link below. Choose the one that best meets your situation.

Change, add, or remove Apple ID payment methods - Apple Support

Create or use an Apple ID without a payment method - Apple Support

Payment methods that you can use with your Apple ID - Apple Support

What happens when you try? If you're getting an error message, what does it say?