Poll instances added to a group without the parent device may or may not sync down to NV. The group gets created and will contain the other type of devices but will not contain the poll instances or if the group is only poll instances it will be empty. When multiple groups are created at the same time usually only the last group will be empty.
In every case the workaround is to go to the NV Console > select the group > on the right select Membership > check the box for 'Enable Membership Matching > Condition = OR > Add, and add the rule/s as needed. Then click Run.
The parent device will get added to the group but only the specific poll instances will have the blue dot and show as 'Included in Group'.