Similar to other Proof of Stake networks, Incognito locks your collateral amount (1750 PRV) for a period of time when you submit an Unstaking request. It helps to avoid exploitation from the outside vectors.
Now, the Unstaking process will complete after the next time you earn. The waiting time can vary due to the random selection of being a Validator. The average time is 5-21 days with the current 2200 stakers. But it might take up to 36 days for the unluckiest case.