Here you can find solutions for some often encountered SvgPublish issues.
The template editor or login screen shows blank (or not responding) what do I do?
The "blank login dialog" issue could be caused by recent the end of support of Internet Explorer.
The authentication dialog and the template editor was initially build using web browser control that is in turn was using internet explorer runtime (support for which has been discontinued)
Now the addin supports the newer browser (Edge Web View) as well. You could turn it on in the settings (screenshot below). Please restart Visio after changing this setting. Please note that turning the option on may require Edge runtime Installation (installed by default with Windows 11 and optional update of windows 10)
Please enable it in the settings