Marketo Opportunities API error

We are trying to build an integration with Marketo and for opportunities API facing an error .

Error: Field ‘mktoCdpSfdcOpptyCampaignId’ not found.

The request works if we do not send mktoCdpSfdcOpptyCampaignId in fields query param.

A couple of other pointers:
- The Opportunity describe API does not have mktoCdpSfdcOpptyCampaignId.
- The Opportunity schema/fields API has mktoCdpSfdcOpptyCampaignId as a non custom field.

We would ideally want to be able to make a successful GET call on opportunities with all the fields that we get from schema/fields.json API.

Could someone please help guide us on this?

Thanks in advance