Roblox Two-Factor Authentication Issue. Can't Access My Account

I'm having trouble receiving the two-factor authentication code in Roblox, and unfortunately, I can't remember the 9-digit backup code. I'm at a loss here—four years of hard work down the drain, and I've been unable to access my account for three days straight. I go by the account name lengpropamda. Roblox, I kindly request your assistance in finding a resolution. I purchased and used Robux, and unfortunately, all my efforts have been lost. What actions should I take? I would appreciate a response.