Plato lived from 428-7 BCE to 348-7 BCE, but Platonism surpassed him for hundreds or thousands of years. Neoplatonism was the dominant philosophical school of late antiquity and exerted strong influence on Christianity until the rediscovery of the major works by Aristotle around at 1200 CE, though there were revivals in the Renaissance and even later.
One very famous counter-argument to Plato's theory of forms was the "Third Man": to avoid the infinite regress, the Form of Beauty must either partake of itself, or must not be beautiful.
How did later Platonists deal with this argument?
It's difficult to imagine that they ignored it. But did they agree on a canonical solution?
According to a modern interpretation, Plato himself suggested a solution by introducing different modes of predication (see here). But did Plato's successors find this solution independently?