I am not able to approve the test charge app subscription for shopify plus development store

[Doug_P]

I believe this is (and has been for some time) a known issue the team is working on:

https://community.shopify.dev/t/unable-to-test-shopify-managed-app-pricing-on-development-store-this-feature-isn-t-currently-available-for-your-store/28199/5