Error when passing purch reqs (STRs) from APO to ECC

In our APO SNP project we are passing purch reqs (STRs between factory and DC) from APO V5.1 to ECC V5 via standard transaction /SAPAPO/C5.

In the CIF log in ECC (trans CFG1) we get error ME083 - 'Enter purchasing group'.

Can anyone advise on how to correct this error?

Thanks in advance...