I'm having this same issue too. Have spoken with a number of agents and all have advised they can't see the availability despite the web site showing there is. Phantom availability I guess. ☹️
This is the error message I get when I try to click through to the payment page:
To contribute a data point, I have transited through DXB dozens and dozens of times and have never had any issues with my EK amenity kits going through security screening.
It's probably just me but I find it very hard to get comfortable in the VantageXL seat, both in lounge and in bed mode. I far prefer the Cirrus and Super Diamond reverse herringbone seats.
As someone who isn't a P1, who lives in 4A/K when travelling in economy, and who watches T-80 religiously, this change is a really awful one to swallow. ☹️
Sure would be nice if they could carry this through to the "regular" non-QBR booking engine, AND also have the booking class indicated in the e-ticket (not just shown only during the booking process).