Have a TA record locator and a BA booking ref. for a Vueling / Iberia two sector flight tomorrow with the return on Sunday.

ba.com offers online check in... goes away and thinks for a bit, but then says it can't do it because it's a partner airline

iberia.com offers online check in, finds the booking and then says it can't do it... reason not given

vueling.com says it's a travel agent booking so it can't do it.

This never usually happens to me on TA bookings (although flying Iberia codeshares is a first for me)

but what is the point of being a Oneworld Emerald able to select seats if the online systems clearly say the booking exists and is confirmed / OK but don't actually function?

That's fifteen minutes wasted and I give up!

Come on OW, you can do better than this...