SecureCRT by Van Dyke uses a proprietary format for private keys called "VAN DYKE SSH2".
We don't support this private key format. We don't know anyone else who does either.
However SecureCRT has the ability to export private keys in the commonly used OpenSSH format, which is supported by edtFTPj/PRO. So if you have a SecureCRT private key, it is best to export it as OpenSSH.