PR can't arrive SRM from ECC with ACC 'U'

HI, experts

  We are working  at  ECC EHP606  SAPKH60606  and  SRM7.02  SAPK-70206INSRMSRV .  Our SRM is in extended classic scenario (ECS)

PR transmission is successful from  ECC to SRM with ACC 'K' or empty value by PI.

But PR with ACC 'U' do not send XML message in ECC.

I know that SRM7.02 support ACC 'U' in SC creation. and I activated the business function as SRM required. also created SC with ACC 'U' successfully in SRM.

what need to do in ECC ?

Please help me on this ?

Thanks !

Jesse.