SBR validation Error: CMN.ATO.AUTH.011 in HandiTax states that the client isn't linked to your agent profile on the ATO portal, the ABN entered for the client has been cancelled, or the ABN is incorrect.
You need to check:
Open the ATO portal and check that the client has been added to your Tax agent number. If the client has been added, remove them and then add them back.
Add the ABN on the ATO portal if an ABN is entered in HandiTax.
Check if the TFN and ABN match in HandiTax and ATO portal.
Check the ABN has not been cancelled: ABN Lookup.
If you have recently processed a CU form for a Trust, ensure you have removed The Trustee For wording from the Trust name. See Why is the client update form being rejected for a family trust.
You can create a Client Update (CU) Form for your client individually, or create in bulk under the Client menu, then click, Batch create Client Update forms.
Note: Contact the ATO for advice specific to your client's circumstances.