UM versions 6.0 and higher have never supported 7-Mode ONTAP - monitoring 7-Mode ONTAP requires UM 5.x.
Copied from the UM 9.5 Release Notes:
ONTAP software supportUnified Manager 9.5 supports ONTAP 9.6, 9.5, 9.4, 9.3, 9.2, 9.1, 9.0, and 8.3.x releases. ONTAP 8.2.x and earlier releases are not supported.