The Key field shouldn't make a difference so long as you're including it in the bulk upsert row properly. Your error states an authentication issue, can you confirm that the account/token you're using has access to update in Table B? I could see one of 2 possible things happening:
- You're trying to update fields that are part of the sync which are not editable
- You have your keys mixed up and so you're potentially trying to add records or not finding the right match which also isn't possible in a sync table.
If you're mapping Record ID#2 to RecordID#2 as the merge field in Table 2 and the fields are editable then there shouldn't be any issues.
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Chayce Duncan
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