Persistently low match rate on AdMob mediation (especially Android) — ironSource bidding didn't help

Hi everyone,

I'm a solo dev running ads through AdMob mediation in my mobile game. For the past few months my match rate has been really low, and it's noticeably worse on Android than iOS.

A few days ago I added ironSource as a bidding network into the AdMob mediation stack, hoping to improve demand but its match rate much less than Admob match rate.

https://preview.redd.it/nwpfilv4yzbh1.png?width=1932&format=png&auto=webp&s=eecb1f30e19c7a2d1325786b141be5f59c81791f

What I've already checked/done:

• app-ads.txt is set up and verified
• sellers.json entries are in place
• I controller ironsource implementation and it works on both platforms.
• I don't have any errors or warning on admob page.

Has anyone fixed a low match rate like this? What should I be checking? Thank you.