In what ways was the third estate prevented from having power before the revolution?

The third estate was made up of middle and lower class of the French population, making 98% of the total population. The other two estates were the Clergy (religious institutions) and the Nobility, the first and second estates respectively. Each group met and were able to vote and discuss the direction of the country. After the Seven Years War, the French economy was decimated and the third estate suffered reparations as the other two estates did not have to pay taxes and were granted certain privileges. Because of the two estates not being tasked with any burdens, the third estate was constantly outvoted and out-voiced by the other two, and this caused a strong desire for a political change from the current circumstances that made it difficult for the third estate to thrive and live.