After spending three months on uTest platform with just 1 test responding (even that was from their own B Team applause), I can say that the platform is dead with hardly any tests to perform.
You will get notifications for other tests but they are mainly to mine data under different pretexts or designs from them.
Also, you can't be sure of any payment even if you do what was required. E.g. If you are looking for bugs in an app, you are supposed to not just find bugs but also to check that no one else have shared the same bug before you. So, you can waste hours to check an app with no reward.