Getting invalid token in Firebase Cloud Messaging

Question

guys, I'm trying to get information about app instance and I'm also trying to subscribe an app instance to a Google Cloud Messaging topic but the problem is whenever I try to use the server key it throws me the error of invalid token and when I try to use the web api key it gives me unauthorized

I've tried it using postman but the results are the same. Can somebody tell me what is it that I'm doing wrong

Here is the screenshot of the request that I'm sending using postman

and here is the screenshot of the request that I'm sending using curl