ACDSee maintains a database that indexes and the photos and contains information about the photos. For this to work correctly photos must only be moved between folders using ACDSee. If photos are moved using Windows Explorer then ACDSee will lose track of them and even though they remain in its database it will not be able to locate them to open.
The location of the database is an exception from keeping all data on the Network drive. This is beacause the network appears to be too slow for ACDSee to operate over the network. Instead we keep the database on the HP laptop's local drive at:
Users/Public/My Photos/ACDCSee Database/Default.
This database must be backed up manually to the Network drive so that backups from the Network drive will pick up the database.