If you haven't used Azure Maps Creator before, I highly recommend avoiding it and not to start using it. At this point, the only people who should be using it, are those who were using it before and are either maintaining what they have or are working to migrate to alternative solution.
As for the cause of the issue you are running into, there is a long list of possibilities. Note, that you have to have your data already uploaded to Azure Maps Creator before it can be opened in QGIS. This plugin doesn't let you create an indoor map from scratch in QGIS (basically, an Azure Maps Creator dataset becomes a data layer of it's own in QGIS). Be sure to follow this documentation if you haven't already: https://zcusa.951200.xyz/en-us/azure/azure-maps/creator-qgis-plugin