External Axis problem

RobotStudio .NET exception: Could not load type 'RobotStudio.Services.RobApi.RobConfigurationExtensionMethods' from assembly 'RobotStudio.Services.RobApi.Desktop, Version=20.2.9116.0, Culture=neutral, PublicKeyToken=null'.

I get the above error when I try to use external axis wizard for an external axis that I created on my own.

I followed the following two youtube videos: 

I followed the exact steps shown in those videos using an earlier version of robotstudio (maybe 2019) and it worked perfectly fine. But the current robotstudio version 2020.4 throws this error even though I follow the exact steps. I used 2020.2 version of the robotstudio and I still get the same error.

Is it some kind of a compatibility issue with the version of robot studio?

Any help is appreciated.