The problem could be related to the FIPS mode enabled.
Remote Desktop Manager uses the AES/Rijndael encryption and SHA-256 hashing algorithms, which are implemented by the Microsoft .NET Framework. If the local security policy on your system enforces FIPS compliant implementations, Remote Desktop Manager cannot run. As a result, you will receive this error message.
To fix this error, configure the Local Security Policy on your system to allow FIPS non-compliant algorithm implementations. Here are the steps:
1.Go to Control Panel > Administrative Tools > Local Security Policy > Open Local Policies > Security Options
2.Disable the option “System cryptography: Use FIPS compliant algorithms for encryption, hashing, and signing.”
Some software (i.e. Cisco VPN Anyconnect) requires the use of FIPS. If this is your case, you must implement the alternative solution described below.
Inside Remote Desktop Manager's installation folder, create a text file named RemoteDesktopManager.exe.config containing the following: