Hello @a.craigQ5FHE,
My understanding is that NTLM is a user profile authentication tool in Windows, so it seems its a system environment issue not a Fusion 360 issue.
There is this troubleshooter tool that can help solve some common issues installing or updating Fusion 360 by using system log files. You also have the option of collecting the log file manually using the steps below.
- Collect the installation log file by access the following path:
Windows: C:\Users\***\Appdata\Local\Autodesk\autodesk.webdeploy.streamer.log
macOS: Macintosh HD>Users>***>Library>Logs>autodesk.webdeploy.streamer.log
- Review the log and the common error codes for Fusion 360 to discover the cause of the installation failure
Please "Accept Solution" if a reply or replies have helped resolve the issue or answered your question, to help others in the community.