When we call POST API's are not working. example
GET API's works well.
What are you using to make the POST request?
oh no @John2578 . Please edit your post immediately and remove the key/password details! Never post those. You'll also need to delete that key and make a new one. I might mark your post as spam (just to remove it) if you don't get to it quickly.
Secondly, if that is the desktop version of postman be sure to click the cookies option on the right hand side and remove all cookies. The online version won't give you that option and will always send cookies. A change request (such as POST) will be blocked for key/password calls with a cookie attached.
The error "Inventory item does not have inventory tracking enabled" is likely because the variant doesn't have "shopify" set to manage inventory. See the "inventory_management" field in the product variant API docs.