Open the SharePoint app catalog. Open the link https://{your-tenant-name}-admin.sharepoint.com/_layouts/15/online/ManageAppCatalog.aspx. Please replace “{your-tenant-name}” with the tenant’s name
Select the app, then click the Deploy button in the ribbon
In the deployment popup, uncheck the check box “Make this solution available to all sites in the organization” & click on the deploy button
Open the SharePoint where the error happening. Click on New button > App
Find the Staff Check In-Out app, then click Add button. Wait a minute, then back to the site contents page
If the app shows in the site content page like the image below, it is complete
