Cannot save pbix or upload pbix to report server

Hey all,

I have installed this on my machine too - upgraded from a Power BI from a year ago, and finally had a window in our schedule to upgrade, and I have gotten this same error.

I have checked the logs, and it tells me there was a timeout on the POST when I am uploading a replace copy or updating a model from the Desktop version (same version as running on the server) and I get the following trying to upload a new model:

2021-08-11 12:52:06.1614|INFO|985|Received request POST /api/v2.0/powerbireports(Path='/Test%20Reports/Test')/Model.Upload| RequestID = s_85650080-125a-4f1c-b634-0545342cf86a 
2021-08-11 12:52:06.1614|ERROR|985|library|Throwing Microsoft.ReportingServices.Diagnostics.Utilities.ItemNotFoundException: , Microsoft.ReportingServices.Diagnostics.Utilities.ItemNotFoundException: The item '/Test Reports/Test' cannot be found.;| RequestID = s_85650080-125a-4f1c-b634-0545342cf86a 
2021-08-11 12:52:06.2395|ERROR|1478|The remote server returned an error: (400) Bad Request.| RequestID = s_85650080-125a-4f1c-b634-0545342cf86a 

And this for updating an existing model:

2021-08-11 11:47:13.5921|INFO|2026|Connection dropped. DOMAIN\AndrewTobin 10.5.253.254: POST /api/v2.0/powerbireports(Path='/Test/Tracking')/Model.Upload, Elapsed time 0:01:39.1772844| RequestID = s_e8d2e6c8-d5c3-406c-831b-566579d97baa 
2021-08-11 11:47:40.9053|INFO|1728|Sending response. Response code DOMAIN\AndrewTobin 200, Elapsed time 0:03:40.2154128| RequestID = s_fe91f816-5794-4909-ab27-04c70527de4d 

One of the differences in the configuration we have is that we don't use the regular server name - we use a server alias, and we wanted that alias to appear on the outgoing emails, etc, so I have set the host on the  Web Service URL and Web Portal URL to respond to http://host:80/reports/ rather than http://machine:80/reports/

When I set it back to accepting "All Assigned" on IP Addresses, the uploads work fine. 

When I set my hostname as the only acceptable URL I get the errors. 

I have tried the May 2021 on our development server as well, to test before changing production, and it uses the "All Assigned" and worked without error.

This configuration worked previously, so I am unsure why updating has broken it, but any resolution you could provide would be appreciated.  And maybe OP has a similar config?