On my existing Qt installation MaintenanceTool update failed:
[9897] Network error while downloading 'https://cdn.qt.digia.com/qtsdkrepository/mac_x64/root/qt/Updates.xml
[14507] Warning: QFile::rename: Empty or null file name
[14507] Cannot rename target to Updates.xml: "Unknown error"
[14509] Failure to fetch repositories.
On a fresh installation (same version of the maintenance tool) it was working ok.