Yes. Bets in Crash can only be placed during the betting phase before the round begins. Once the countdown ends and the multiplier starts increasing, no new bets can be added to the current round.
Make sure to confirm your bet and configure any settings, such as Auto Cashout, before the betting period closes. If you miss the betting window, you can use the Bet Next Round button to place the same bet with your selected settings in the upcoming round.