Error when trying to send an invoice in SUS to ECC
I'm implementing MM-SUS in SRM 7.0 & ECC 6. We've been live with POs for a while, but now I'm trying to get GRs, SAs and invoices running (we're not using ASN functionality in SUS). I thought I'd gotten all of the config set up, but when I try to send an invoice in SUS, I get the error "Active status of document SUS Invoice 50000xxxxx is Incomplete . No changes are possible"
I've followed the config docs pretty closely, and I've added BUK and ACS entries in the org structures. But nothing's happening. I'm sure I'm overlooking something obvious, but I'm hoping someone can point it out to me.