While Windows Activation needs internet to work, you can also activate Windows over the phone. If you are getting an error code 0xC004F02C it means there is an issue with the data you received over the phone. The full error message says

The Software Protection Service reported that the format for the offline activation data is incorrect.

It applies to both MAK and KMS keys. To fix this, you need to verify that the CID is correctly entered. When you make a call for activation, you get a Confirmation ID from Microsoft. You need to enter the same to activate your copy. If you enter the data incorrectly, then you get this error.

It is best to call Microsoft Support Center.