Are you sure that you copied that correct wallet.dat file? Because most cryptocurrencies wallets have a wallet.dat file, so if you try to open wallet.dat file belonging to some other cryptocurrency apart from KMD, it might throw an error. Other chances are the wallet.dat you copied the first time is corrupted or you entered the wrong password to open it. Since the error shown is very generic, I don't think that anyone here could help you, it is better to contact their support.
New wallet was not encrypted yet because once i created i moved to old wallet for a transfer once transfer was done i moved to new wallet then this error occur. If the file .dat is corrupted is there any chances to access it ?
I am not sure if you can restore it as I not much of a technical guy. I would advise you to take a backup of the files and then contact their
discord support regarding the issue. You might get some help there.
Also, try this method, it might help not sure though -
https://www.youtube.com/watch?v=D7Qsm8V3Lyk