The Maplex Label Engine key numbering labels do not rotate with a rotated data frame, and there is no way to set a rotation for a key numbering group.
Last Published: January 21, 2019ArcGIS for Desktop
Bug ID Number
October 31, 2014
March 30, 2022
ArcGIS for Desktop
Operating System Version
This issue was not reproducible when tested by the development team. Issues may be given this status when they cannot be reproduced or are no longer relevant in a development version of the software, but a specific fix was not installed to address the issue. The issue's Additional Information section may contain further explanation.
In ArcGIS Desktop Pro 10.7, the key numbers now rotate with the data frame as expected.