It is possible in some instances to experience a rejected bet. This most often occurs when playing live dealer games. A rejected bet will be accompanied by an error message/pop.
The most common reasons for a rejected bet would be a poor/weak signal strength, a geolocation issue (such as close proximity to the border), or exceeding a maximum bet limitation while participating in a bonus.
No matter the cause for a rejected bet, your money is safe. If a bet is rejected, the funds you attempted to wager were not accepted and they will be returned to your balance. It is not possible to receive any winnings from a round where a rejected bet has occurred.