Known Issue ID: 15703
The camera may not recognize some Sigma lenses (for Canon mounts). This issue has been reported with the Sigma 85mm, Sigma 50-100mm, and Sigma 135mm ART lenses, but may affect others.
Found in Firmware Version:
Target Firmware Fix:
When attaching the lens, slowly twist the lens until it snaps into place. If the camera still does not recognize the lens, remove it and slowly reattach it again.