Can I get my GRE essay rescored?

Yes. ETS offers a Score Review service for the Analytical Writing section. The fee is $60, and you must request it within 6 months of your test date. An independent reader will re-evaluate your essay. If the new score differs from the original by more than 1 point, the new score replaces the old one. If it doesn't differ enough, the original stands. Given the cost and the narrow window for a meaningful change, this is only worth considering if you believe something went wrong with your original scoring.