SSMS 2017 - connection error on one server only

Question

I am having an issue with SSMS 2017 (latest build) on a single server only.

The set up is this: - In preparation for upgrading SQL Server from 2012 to 2017, we have restored our two servers into an isolated network. This allows us to have the servers with same names, IP addresses, and same domain just in an isolated network completely separated from the main domian. There is no internet access on this network.

The two servers are the main DB Server & its DR server. Log shipping & restoring is set up between DB & DR Servers.

I can install SSMS 2017 on the DB Server with no issues and on this server I can connect to the SQL instance on the DB server and to the DR server with no issues at all.

SSMS appears to install fine on the DR server, but when I try to run it I get the following error:

Method not found: "Void System.Data.SqlClient.SqlConnection.set_AccessToken(System.String)". (Microsoft.SqlServer.Management.Dac.DacWizzard)

I should note that this only seems to happen with SSMS 2017 as SSMS 2012 continues to function correctly and I can install SSMS 2016 and that also works fine.

Any help or advice is greatly appreciated,