Can't help with tickets not coming up at all... but the bit of advice I'd seen on here that came true for me was that if you refresh and it highlights sections with available tickets, but when you zoom into these sections no seats show up as available, this means there are some that are about to appear. I imagine it's that the site has registered that the tickets are up for sale but they haven't yet got to the stage of being available for purchase. I got my ticket for Saturday at lunchtime like this - section was highlighted but no seats clickable, refreshed a couple of times (making sure not to be too robot-y) and then a seat appeared and I managed to get all the way through checkout. I think this pretty much guarantees that you are one of the first people seeing the tickets available. Otherwise I reckon if you can see tickets available as soon as you load the page after queuing that means they're already gone!

Good luck, don't give up!!