I have updated Power Bi to the latest version of September, but the problem persists and new visuals are not downloaded, it indicates the following message: The custom visual could not be imported. This may be a temporary problem. Try it again later. If you still have a problem visit support.powerbi.com and report the problem.
They cannot be downloaded from the website either.
You mean you could access AppSource but couldn’t import visuals from it? Is this issue happening on a specific visual or all the visuals? If you try with older version Power BI Desktop, will you also get this issue?