"API is not enabled for this Organization or Partner" error is shown when integrating with SalesForce

I am getting this error:

API is not enabled for this Organization or Partner

What exactly does this mean?  Is this coming from Salesforce?

This error is being sent from SalesForce. It basically means that you would need to upgrade your plan with them because the API (Web Services API) that this communication is done over requires you to be on Ultimate or Enterprise plan for you to be able to utilize it.

If you are not sure what exactly is needed, or want to see if it is possible for you to have that access on your current plan, you should contact SalesForce support.

To confirm, I have also tried to create an integration with them just now, and it is working properly, so once you talk with them and resolve this on their side, you should be able to simply set everything up with few clicks :)

Do of course let us know how it all goes.