I was able to test book a OW JFK-BRU-TLV,
as others have mentioned dealing with the EY call center is like the wild west, each agent have their own set of rules & I actually found that the indian agent in AUH was more competent then the ones in manchester.
The maddening part is that theres no way of knowing what availability EY has access to. It doesn't match ExpertFlyer, AC or UA
I actually found that even SQ wasn't matching UA availability which leads me to suspect the problem lies with SN