Error connecting to PostGresSQL db

[JR2018]

Hi there, 

I have searched the preexisting threads related to PostGres connections but have not found one with the same issue. When I open Power BI desktop, i click Get Data and then i select the PostGresSQL database option and enter the Server Name and Database name. I then get the error below. 

Details: "An error happened while reading data from the provider: 'Could not load file or assembly 'System.ValueTuple, Version=4.0.3.0, Culture=neutral, PublicKeyToken=cc7b13ffcd2ddd51' or one of its dependencies. The system cannot find the file specified.'"

Any advice on this would be appreciated. 
THanks