Until few days ago i used this url to create a transaction:
https://api.paymill.de/v2/transactions?token=XXXX&amount=XXXX¤cy=EUR&client=client_XXXX
And now i am getting a error:
Return Message
Error calling API: The remote server returned an error: (403) Forbidden.
I think is something related with the data format.
you have to send this as a POST request to the Paymill API. See examples at: https://www.paymill.com/de-de/dokumentation/referenz/api-referenz/#create-new-transaction-with
Also check if your credentials (Private API Key) is valid.
Matthias