We can only add transactions to Constituent accounts, see What is the difference between roles. So, if this account is for a User or a Tribute we will need to add a role to this account. We can check to see what type of account it is by looking in the top right corner above the Account Number.
Screenshot of Tribute account role

If this is not a Constituent account we will need to add that role:
  1. Click Account Settings
  2. Click Add Role
  3. Mark Constituent
  4. Click Save