Shopify API return "API Access has been disabled"

Shopify Partner
23 0 1

One of our customers installed our app but when we try to fire any API it's giving an error "API Access has been disabled".
Could you please tell me why we are facing this issue?

This type of issue possible from the Shopify side? (

I want to know why this issue generated and how can I fix it without uninstall and reinstall the app?

Also, there is any surety if uninstall-reinstall will fix this issue?

Thanks & Regards,
Tejash from Identixweb