Did you exchange the returned ?code for an access token as per step 3?
3) On your server, get an access token by making this request:
?client_id=<your client ID>
&client_secret=<your client secret>
&code=<authorization code received above>
&redirect_uri=<your registered redirect URI>
Here is a sample request:
Fortunately, I sent the request from the beginning and received the token in the form of JSON. By the way, how can I use the API using the token I received now?
The status of 401 is the result of the api requested by axios.get().
Below is the response I received after running step 3.