Reason of Error "Public Sign up is not enabled" while importing XML-Backup?

[David Heunisch]

I've tried to import a XML-Export. After unzipping the Import-file the import stops with the following error message: 

{"errorType":"PublicSignUpDisabled","message":"Public Sign up is not enabled"}

Is there any special authorization requiered? How can i fix the error?

The XML file is from another confluence instance. Can this be the reaseon for?

Thanks!

David