HI Macdonald,
I remember facing a similar issue, can you try switching to "https" and see if it works.
This may not be a permanent solution, but I guess it should help you.
Example: When you start transaction SOLMAN_SETUP, it opens a browser in "http" i.e http://<hostname>:<port>.... just change this "http" to "https" and see if it works.
Regards,
Leela.