When adding ordinance information for the sealing of a child to his/her parents, the parents in the Legacy family file must first be matched to the parents at FamilySearch. You can tell that the parents are not matched because there will be no FamilySearch ID for the parents on the Legacy side of the Share tab and there will be no arrows for the Sealing to Parents on the FamilySearch side. Once the parents are matched/linked the arrows will appear.
First click the Refresh button on the right side above the FamilySearch person and then click the Reload button to reload your Legacy person. Sometimes Legacy FamilySearch is holding on to old data and this will clear it out.
There also must be no red links. See the article "A red link shows on a person in Legacy FamilySearch".
If the child or the parents on the Legacy side of the Share tab have a different FamilySearch ID than what shows on the FamilySearch side, and they are the same people, unlink the them on the Legacy side. To do this click on the transfer arrow button by their name on the Legacy side and select Unlink from the popup screen. Next relink/match them to the child or the parents on the FamilySearch side. Now you can transfer the sealing ordinance.
Also check to make sure that the list of Legacy persons on the left side of the screen is showing everyone. Remove any filters you have set and then click the Refresh button in the Current Filter area at the top of the Legacy persons list.
