I'm not sure I got your text right, but from my understanding , can't you just tell them you need to complete the first milestone before moving on? Or have them place a new order for this task to make sure you get paid. What do you think?
Same thing happened to me. Since I became a level 2 seller I've only been able to get orders through buyer requests or from past clients.
Clients with constant monthly orders are my motivation to still be on Fiverr.