Hi Stephen Gillan,
Following up on this question, we were able to get the Manufacturing Apps Dev Kit login screen issue resolved by switching to Chrome. I cannot recreate this issue here, but I suspect either Internet Explorer was not the supported version (IE 11 or higher), or the security settings for IE were preventing the connection from occuring. For reference, here are the System requirements for the Manufacturing Apps install:
Can you confirm the solution I describe above by selecting "Correct Answer" for this post in the Community thread? Please be sure to let us know if any issues arise, or if you have a question about anything else.