OpenRent deposits are held in a government approved custodial deposit protection scheme and your deposit is controlled through your landlord's account. As it is the landlord's responsibility to return the deposit to the tenant, you will need to speak to them directly to arrange the deposit to be released.
Alternatively, if you are unable to reach your landlord, you can request a repayment directly from the deposit protection scheme's website here:
Need help finding which deposit scheme your deposit is with?
You can check which deposit scheme your deposit is protected with in your tenancy agreement.