To login to Internet Advancement you must be the unit leader, Chartering Organization Representative or Committee Chair of your unit on your official roster (not just in Scoutbook.) If not one of these three, you will need to be designated in Organization Security Manager at my.scouting.org as a Key 3 Delegate or an Advancement Chair by someone holding one of the three positions above. To make such a delegation, see the guide here.
For more on Organization Security Manager see: https://help.scoutbook.scouting.org/knowledge-base/assigning-a-key-3-delegate-or-other-position-in-my-scouting/
NOTE: If you are using Scoutbook for your unit’s advancement, you do not need to use Internet Advancement. Scoutbook users should not use Internet Advancement