Don’t look at the lack of reviews as a problem – see the opportunity. You got paid for your skills. Someone hired you because they wanted what you have to offer, you delivered what they ordered, and you got paid. There is nothing wrong with that.
There will always be future opportunities to earn reviews.
Look at it this way: Does your favorite barista gain a public review after she hands you your coffee at your local coffee shop? Does the cashier at the grocery store gain a public review because she was friendly while she rang up your purchase? Not likely. You are a freelancer in demand – people want your services. Reviews are not, nor should they ever, be guaranteed – they are a bonus for work well done.
You’re not going to get reviews for most of the orders you deliver. And that’s okay. Move on to the next order, and deliver top quality work that could earn a positive review – if the buyer chooses to post one.