Hi Rob,
The post you added to is 2 years old, and there have many Simlink versions since.
You might like to reset you Simlink using Unable to sign into Simlink - #16 by vishalahir.
If still an issue please upload your Simlink dlog files from c:\Users\username\AppData\Roaming\Navigraph\Simlink\logs\ and our Simlink experts can review if there are fixable issues.
Cheers
Ian