shopify post purchase extension

Question

Hi I'am trying to test a post purchase extension.

I tried the following steps:

• registered my post purchase extension with the code provided
• Served the extension using shopify extension serve
• Installed the local app extension to firefox
• Updated the firefox extension with the ngrok url
• Tried to checkout from my development store -No redirect occurs to the extension and nothing in logs, checkout goes directly to thank you page

if someone experienced could make a basic guide over this topic, that wold be awesome :)