Popunder volume in Tier-1 countries is terrible lately — anyone else noticing this?

I run popunder campaigns for dating offers in the US and UK. Over the past few months, I've noticed that my usual networks just don't have the volume anymore. I try to scale my daily budget and I can't — the inventory just isn't there. My campaigns stall out around 200−300 per day when I want to spend 1000+. Is this a problem across the industry or is it just my networks? Where are people getting real Tier-1 popunder volume these days?

This is a supply problem on most networks. They don't actually own the inventory — they resell leftovers from other exchanges. The network I use owns their supply directly: https://www.advancedtechnologyholdings.com/ They process over 4 billion ad requests daily and their Tier-1 fill rate is 96%. I scaled my daily budget from 200 to 1400 without the volume dropping at all. If you need real US and UK volume, that's the place. Their popunder quality stayed consistent even as I scaled.