Please note you need an admin account to resolve this.
There are two likely reasons you can’t see the app in App Launcher.
1. The custom domain isn't properly set up.
Use of Scan to Salesforce requires you to have a custom domain. Please go here for more information.
2. The permission set isn’t properly assigned.
Go to Setup > Administration > Users > Permission Sets and find Scan to Salesforce. Assign the permission set by using Manage Assignments and then choosing the relevant users.