There are a couple scenarios described below that could occur that will prevent you from connecting successfully using RDP. If your issue does not fall under either of the cases below, please reach out to support.
Wrong Domain
Description: If you are unable to connect with RDP but have verified that it is enabled in the GRIDSMART Device Manager, you may have an issue with your RDP configuration settings. For User Name you should include either the specific GS2 Serial # for the device you're attempting to connect to (ex. GS2-3751) or `AzureAD`. Please see examples below for valid configuration settings.1p
--OR--
To modify User Name settings if they are not correct, click on 'Show Options'. Edit the portion before the GRIDSMART user to include either the specific GS2 Serial # for the device you're attempting to connect to (ex. GS2-3751) or `AzureAD`.
--OR--
If you have verified that your configuration settings are correct and you are still unable to connect via RDP, please reach out to support.
Workaround: Enter valid User Name settings as described above.
"CredSSP encryption oracle remediation" error
Description: If you encounter the error "CredSSP encryption oracle remediation" when attempting to RDP to your GS2, this is likely due to a Microsoft security setting.
See this microsoft support article for more information.
Workaround: As a workaround, you can edit your machine's Windows local group policy (gpedit.msc) if you have admin privileges and Windows Pro Edition. Please see this link for more info article with detailed steps. 
Under Computer Configuration -> Administrative Templates -> System -> Credentials Delegation, there is a setting "Encryption Oracle Remediation". Its default value is "Not configured". Change this to "Enabled", and set "Protection Level" as "Vulnerable". 
If you do not have Windows Pro Edition but you do have Admin Privileges, you can alternatively open a command prompt with admin priv. and use the following command.
reg add "HKLM\Software\Microsoft\Windows\CurrentVersion\Policies\System\CredSSP\Parameters" /f /v AllowEncryptionOracle /t REG_DWORD /d 2
Version(s) effected: All versions that use RDP
Fix implemented: N/A
Relevant tickets: N/A