Submit a bug report. Fizzer is usually super responsive.
I tried this approach once and the only (and understandable) response was, that this is not something he can control, if it is just down to Google not serving any ads at this point. So, yeah, if you have an issue, file a report, but if it is likely that it's just ads, try the before mentioned tricks like force stopping the game (or switch to Apple, in case you use both Android and Apple (those people exist??)), other than that, "try again later". The ad boost is nothing that you were promised when you signed up for the game. It's a nice-to-have. Don't bother Fizzer when he could come up with new and nice game features instead at the same time. ;)
PS: This also comes down to your region, because ads are sold for a specific audience. If you live somewhere, where no ads were provided for (is there an option for Antarctica-based ads for example? sure, this only applies to a few researchers), then the pool of ads to draw from is rather small and probably more depleted then for the US of (Central) Europe. I feel for you if you hadn't had a chance to gain the ad boost for days, I only ran into this problem once for a few hours and this was already some months ago. But again, Fizzer can't help you when living in (definitely exaggerated, wherever you live ;) ) an almost deserted area that no company wants to provide ads for.
Edited 5/20/2021 10:20:00