The Paypal API doesn't recognize my Client ID and Secret I got from https://developer.paypal.com/developer/applications/ I wanted to include a server side checkout according to this tutorial https://developer.paypal.com/docs/archive/checkout/how-to/server-integration/ When I do the request to https://api-m.paypal.com/v1/payments/payment I always get a 401 Error with the message "Authentication failed due to invalid authentication credentials or a missing Authorization header.". I checked multiple times if my credentials were correctly included into the request. I also tested the endpoint in my server environment and as well via Postman. I also tried the route https://api-m.sandbox.paypal.com/v1/oauth2/token/**bleep** to exchange my credentials with an access token and got the same problem. I also tried to create multiple Sandbox and Live Accounts and always got the same error. Has anyone an idea what the problem could be?
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