How do I change the sentence "this candle is made of natural soy wax" into an active voice? Also, can someone please explain why Grammarly considers "is made of" a passive voice misuse?
There is nothing wrong with
This candle is made of/from natural soy wax.
To make it in the active voice, you might use
or less precisely/accurately
has / contains
First ask yourself why you want to change the sentence. However advanced Grammarly is, it's still far from giving sensible hints all the time.