My backoffice won't load. When I browse to www.mydomain.com/umbraco it forwards to www.mydomain.com/umbraco#/content and I see this.

My developer console shows several errors:

I read a stackoverflow post that said clearing cache/cookies would do it, but that didn't work for me.

I read another forum post that said timeout was set to 0...mine is set to 60.

After some testing I found that some 301-redirects I had setup in web.config were to blame. The offending 301-redirects look like this one:

<rule name="Redirect legacy projects" stopProcessing="true">
          <match url="legacy/(.*)" />
          <conditions />
          <action type="Redirect" url="https://www.mydomain.com/about-us/legacy" appendQueryString="false" redirectType="Permanent" />
        </rule>

I'm unclear what about this 301-redirect would pose an issue to Umbraco.