I'm upserting Account Contact Relationships the first load, works fine and we are upserting on a customer external ID field. When the upsert is run a second time - we see this error in the logs:
"INVALID_FIELD_FOR_INSERT_UPDATE:Unable to create/update fields: AccountId. Please check the security settings of this field and verify that it is read/write for your profile or permission set.:AccountId --"
This occurs regardless of whether we use the Salesforce ID for the Account ID, or we use the lookup field, based on our source data.
In this scenario, we are not changing the Account ID, the same data is being upserted in each batch (at some point in the future, we intend to do a differential load, but currently we are limited to just running a full load)
Can anyone shed light on to why this is occuring?
The Upload is being done as my user, which has full Admin privileges.