Cannot get self-assessed Tax to apply automatically in AP

I have referred to Doc ID 948414.1 and followed most of the steps with additional conditions around Bill From/Ship From EU country but I cannot get self-assessed tax to calculate automatically on AP invoices. It calculates standard VAT but that is not correct for invoices from the EU. I can manually update the tax in tax details for Self-Assessed but I need it to be automated. I don't know what is missing as i have done this type of configuration before and it's worked. I'm wondering if patches are required to get this working as our client is not fully patched up