Solution 1: Changing Security of RDP in Group Policy Editor (Server side)
Step 1. Go to the Start Menu and search for Local Group Policy and open up Edit group policy.
Step 2. Start to navigate to the directory listed below:
Computer Configuration > Administrative Templates > Windows Components > Remote Desktop Services > Remote Desktop Session Host > Security
Step 3. On the right hand side, find Require use of specific security layer for remote (RDP) connections and open it.
Step 4. If this is set to Disabled or Not configured, set it to Enabled and then for Security Layer and choose, RDP.
Solution 2. Disabling Network Level Authentication (Server Side)
Step 1. Go to File Explorer and right click on This PC and then click on Properties.
Step 2. Click on Remote Settings on the left hand side.
Step 3. Under the Remote tab group un-tick the checkbox Allow connections only from computers running Remote Desktop with Network Level Authentication (recommended).