Hello,
Activating the deposit bonus has some requirements, and one of these requirements is that you are not allowed to play Stake Original Games while the Rollover is activated.
Also, you will not be able to withdraw money until you lose your deposit and the deposit bonus amount and/or fulfill the rollover requirement. If you do not want this to happen again, contact support and ask them to deactivate your deposit bonus.
You can read more about the "Deposit Bonus Requirements" here > https://stake.com/policies/deposit-bonus-requirements
Regards