Hi there 
I’m new here and new to android development. About a month ago I published my first app to Play Store and included AdMob banners. For a while everything seems to be running fine, with increasing numbers of downloads my impressions also increased and I got also a bit of revenue (but its still almost nothing).
I have 3 banners in my app, one banner for each fragment page (swiping through them with Action Bar). Refresh rate has been set to 120 s, yesterday if set it to 60 s, which seems to make it even worse… I dont use mediation and the only filters set are ‘Sensitive categories’ (black magic, ***** pills, etc… are filtered) just AdMob with the “Optimized” setting on by default and no eCPM floor setting for it.
At the beginning of the day my match rate (is ‘match rate’ the same like ‘fill rate’, seems Google has renamed this field?) is about 100% and seems to be normal. Then, the number of ad requests raises dramatically, while match rate drops down to ~5%… ??? I really dont know why, but obviosly something must be very wrong with it.
Heres the graph for the last 30 days, trouble seems to start around Aug 17th…
And this is from today 
(the interstitial has been removed meanwhile, the request come from older versions)
This is only for a few hours, indicating today will be even more worse than yesterday again
What happens to all those ad requests and why??? The strange thing is, everytime I open my app, I get ads served…? So, I feel a bit cheated…
Please help me guys, how can I get a reasonable match rate like it was before???