Unable to pay as Your account my be at risk!(1138)

Looks like a payment error (?).

You may need to have a payment method on file, even if the app you want to download is free.

Check which payment method you have on file 

See also -> Payment methods you can use with your Apple ID

Payment methods you can use with your Apple ID – Apple Support (UK)

You can also use your Apple ID balance as payment method:

Add money to your Apple ID balance

Add money to your Apple ID balance – Apple Support (UK)

You can also contact the app developer -> How to contact an app developer – Apple Support (UK)