My App Store "Double-Click to Subscribe/Download" button doesn't work

Hi PipsCraigg,

Welcome to the Apple Community.

Wondering if you are also signed in to your iPhone with your Apple ID

Sign in with your Apple ID - Apple Support

Else:

It seems Apple requires a valid payment method in your Apple ID account,

this is just for the first time you use the App Store, or iTunes, and even if you only download free apps.

If this is the issue:

Apple support have articles online (links below) that may help.

Check the payment methods that you can use with your Apple ID:

(Scroll down to find your country or region)

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

Then: Add a payment method to your Apple ID - Apple Support

How to: Get apps in the App Store on iPhone – Apple Support

________________________________________________

Troubleshooting if needed:

If you can't open the App Store or iTunes Store, buy content, or edit payment information - Apple Support

If you can’t download or update apps on your iPhone or iPad – Apple Support

If your payment method has been declined in the App Store or iTunes Store – Apple Support

App Store Support Website

App Store - Official Apple Support

All the best :-)