i bought robux for $20 2 times and i did not receive anything on my account on roblox i...

I just experienced the same issue. I bought the $0.99 88 robux option from the Roblox application through Microsoft and it also said that something went wrong and that I was not charged. Turns out I was, and I never received the robux. Based on what I've read, they don't accept refunds for in-game purchases like robux. My suggestion is to buy directly off of the Roblox website rather than through Microsoft. I've never had any issues making purchases directly from Roblox. Huge disappointment from Microsoft. I would steer clear of making Roblox purchases through Microsoft from now on.

Oh thanks alot Jesse E and also if I use one microsoft account to get robux on my roblox account and then use another microsoft account to get robux on the same roblox account what happens?

Punish your boy and tell him to NEVER make purchases again without allowance.. And I doubt you can get the money back because your son would've payed for the ROBLOX virtual currency known as robux and he as probably bought clothing and game passes with these
robux so nor Microsoft or the ROBLOX team will be able to get the robux back because they are unable to take the bought items off his ROBLOX account. Also change the settings on your Xbox to make it require a passkey or your password when making a purchase!

I didn't get the robux after i signed into my roblox account on my friend's xbox?

Hello, thanks for replying! Yes, my 400 robux purchase was not added to my roblox account that had the email that I purchased it in verified, The robux purchase as well had gone through.