Only the Admin of the Ad Account can successfully connect to Shoelace. If you are not sure about the permissions you have on the Ad Account, follow these steps below to find out:
Search for the ad account you are trying to connect
On the right pane, under your "People" find your name
There are three permissions on an Ad Account: "Analyst", "Advertiser" or "Admin"
If your role is currently set to "Analyst" or "Advertiser" on the Ad Account, you will need to contact the Admin and ask them to make you an Admin as well. Alternatively, you can ask them to log into Shoelace and establish the connection themselves.