No offers available. Check back soon. - Driver Amazon Flex Employee Review

I've been "employed" (?) by Amazon flex for a few weeks now and I'm yet to complete my first shift. The app often gives me notifications that there are offers (shifts) available for me (specifically reserved for me, no one else), yet when I open the app I'm greeted with "No offers available. Check back soon". Even Amazon's help section tells you this is likely to happen because there are so many drivers now that shifts are so rare. It goes on to say I should constantly (as in for 10 hours straight) refresh the app in the hope that I catch a shift being advertised. This is not a sustainable means of employment. I'd be better off working freelance for one of the many other courier companies on a lesser wage.