Hello Campbell,
Apologies for the late reply. We had a glitch where this one was missed. Maybe the forum needed a coffee to wake it up! :-)
Thank you for providing the request ID and logging with important info redacted in a question like this. It makes it much easier to look up. I see that our back-end is saying: CampaignError.SELECTIVE_OPTIMIZATION_CONVERSION_TYPE_OWNER_ACCOUNT_INVALID As you already see, it's referring to field_path: "operations[0].create.selective_optimization.conversion_actions"
I took a look into the account where I think this request was made. I don't see that conversion action ID in that account. Please double-check the conversion action ID to make sure it's in that account and retry the request. Perhaps, you meant to use another conversion action or a different account with that request. If the request doesn't work after trying again, please reply to this thread or reply privately to author.
Thanks,
Nadine Wang, Google Ads API Team