Linode API UNAUTHORIZED response

Firstly, if you're using our cli to make api calls you'll want to ensure you have the most current version. To update:

Mac OSX:
brew update
brew upgrade linode-cli

Debian and Ubuntu:
sudo apt-get update
sudo apt-get upgrade linode-cli

If you believe the issue is on our end, that is to say our api service is unavailable, you may want to subscribe to our Linode status updates to know when routine maintenance is being performed that may impact your application.
https://status.linode.com/

If you're version isn't the issue, you'll want to verify that you have access to the api. Try running the following command to test connectivity:
telnet api.linode.com 443

If you run into issues with the above command, try the following to force the connection over IPv4:
telnet -4 api.linode.com 443

You've successfully connected if you receive output similar to:

Trying 69.164.200.203...
Connected to api.linode.com.
Escape character is '^]'.

If you are able to connect to our api, reach some endpoints, and are able to run some linode-cli commands, but the UNAUTHORIZED error persists, then its also important to note that some endpoints require authentication.

All endpoints affecting your Account require either a Personal Access Token or OAuth authentication (when using third-party applications). So it's important to ensure that you've set up your access and authentication correctly.

Here's our guide for setting up an access token and authenticating your api requests.
https://www.linode.com/docs/platform/api/getting-started-with-the-linode-api/#get-an-access-token

Additionally, the official documentation pertaining to authenticated calls outlines our authentication scheme and which calls require proper access tokens.
https://developers.linode.com/api/v4#section/Access-and-Authentication