Trying to insert about 50 records into the opportunity object within a sandbox using data loader and receiving the above error. I've made sure that this field contained active user IDs and then modified all the records to have my user ID listed under this field, but to no avail. Any idea what I should be checking to get past this to successfully insert? ##Dataloader
I know this is an old thread but wanted to share how I got through this issue as well in case it helps anyone.
The ultimate root cause was that there were a couple of flows that were updating the Account with the Owner ID - but since the Contact records in question were owned by inactive users >>> that was causing the invalid OwnerId error on dataload.
So I turned those off, did the dataload and turned them back on and it worked.
