I need help!!!!

I really need some form of advice to deal with a problem. I am a freelancer and over the past 2 weeks, I bid for some projects here on up work. both buyers sent me a separate email with a contract which I signed and a start date. With the first one, the start date was meant to be on Wednesday 1st of April. I have been trying to trace the buyer but to no avail. The buyer wouldn't respond to any of my messages. The recent one also (her name on PPH: Patricial S.) sent me an offer letter and a contract, which I signed, however, this buyer has also ignored all my emails and not replied. I do not know where I stand or how to deal with it. Can anyone help me?