This was the problem indeed. I thought I had chosen JSON the first time and chosen my timestamps. Did it again now and it works beautifully 🙂 Not sure what I did wrong the first time, but probably some basic mistake.
The answer below from @tiagofbmm should work, but it's not as efficient as filtering in the base search. I'm surprised that the query you posted isn't working, because such structure works in my environment. Does it return no results at all, or just fail to return some results you know it should be returning?