Logging into SDK in Visual Studio using a different machine

Hi, probably a newbie question...
I have a new PC, have set up Visual Studio and downloaded the SDK. When trying to connect to my instances I get an error: 'The request signature we calculated does not match the signature'. I'm not calculating anything that I know of and have copied and pasted the input fields from the previous machine.
I set this up on the 'old' machine over a year ago and can still log in on that one and deploy my ASP.NET/RDS application. However, I'm at a loss as to why the copied and pasted credentials won't allow me to log in as all I've done is got a new machine.
Is there a setting or something else I need to change?

https://docs.aws.amazon.com/sdk-for-java/v1/developer-guide/credentials.html