At this point in time, embed to web has not been enabled for the ArcGIS Maps for PowerBI visual. We have logged an enhancement on this ENH-000130489: Add Publish to Web support to ArcGIS Maps for PowerBI visualizer in PowerBI Online, which has the current status of In product plan.
While I am unable to comment as to when this will be resolved, I am able to say that the product team is very much aware of this limitation, and is working diligently with Microsoft on a resolution. If you are able to do so, I would encourage you to log a case with Esri Tech support to add your account to this enhancement.
Recently the way ArcGIS for PowerBI works with web embedding has changed, reports must now conform to the prerequisites listed here:
Once you fulfil the requirements, your report should work again.