NOTE: you should contact your administrator as this is an issue that can generally only be resolved by an administrator. >
FollowCol Dashboard saves user data to the Add-In/App Web which is a special SharePoint site that is generally hidden but known to administrators. If FollowCol Dashboard users do not have at least "Contribute" permissions on the Add-In Web they will not be able to use FollowCol Dashboard because they will not be able to save a FollowCol. Where the Add-In Web is physically located is dependent on how the Add-In is installed, with either Web Scope or Tenant Scope.
If the Add-In is installed to an individual site, generally by a Site Collection Administrator, the Add-In will have Web Scope. This means that the Add-In Web is located within the same site as where the Add-In is installed. Any user that has at least Contribute permissions to the site will automatically get Contribute permissions to eh Add-In web therefore these users will not encounter any issues when saving a FollowCol. However, users with only Read permissions will not be able to use FollowCol Dashboard because they will not be able to save a FollowCol.
An Add-In can be installed with Tenant Scope by a tenant-administrator by installing the Add-In in the Add-In Catalog and by following a particular deployment procedure. With a Tenant-Scoped Add-In the Add-In Web is within a site in the Add-In Catalog. Generally users only have Read permissions to the Add-In Catalog and since the Add-Ins inherit the permissions of their parent site users of FollowCol Dashboard will not be able to save FollowCol data. Your administrator must provide a way for Add-In users to have Contribute permission on the Add-In Web(s) of the Add-In catalog.
If FollowCol Dashboard cannot save to the Add-In/App Web the following message will be displayed:
For more information on Add-In/App deployment/installation and scopes see Tenancies and deployment scopes for SharePoint Add-ins