@Jazmine20 That's really terrible of the host: extremely sketchy. If they agreed to the arrangement with allowing you to reschedule to 2022 via Airbnb messenger, contact Airbnb and show them what's happened and request a full refund. I like contacting Airbnb on Twitter @airbnbhelp. It's also easier to reference the conversation you had with the host. I would avoid rebooking with the same host if I were you, as they don't seem very ethical.
One thing for the future, though: I would not have waited this long to follow up with the host and/or Airbnb when your request wasn't accepted. The sooner they accept a change, the sooner others can book the dates, so it shows that he probably wasn't acting on good faith from the get go.
Good luck! I hope you're able to get it sorted out.