There are several reasons why you may not be able to withdraw money from robinhood.

Can i withdraw buying power from robinhood. You may not be able to withdraw money while your account is restricted. I realized why i couldn't. Why did my buying power go up on robinhood?

On robinhood buying power can also be affected by the time it takes for money to be added to the account. By this rule, these uninvested funds must stay in your account for at least 5 trading. Select “transfers” to go to the “transfers” page.

After logging in robinhood.com, click the “account” menu in the top right to bring up the menu dropdown. Brokerage cash may be margin used, and if you have buying power through margin that would be why you can't withdraw it. You have to wait a couple of days if you sell stock in order to withdraw it.

The most common reason is trying to remove funds before the settlement period.