It is very simple. The EU have broken the WA by not "using their best endeavours, in good faith to negotiate expeditiously their future relationship with the UK" If the EU had honoured their obligations it might have been possible for them to open their outpost in NI. But they can't cherry pick or have their cake and eat it.
They broke the WA, it is dead - not just bits of it, all of it. No deal here we come, yippeeeee!!!