You have SQL sever installed on Windows workstation (Windows 8 or Windows 10). You create a protection plan and enable application backup.
Server quota is used for this machine or, if you don't have an available server quota, backup fails.
Application protection is part of server licensing model; application-aware backup is not available in workstation quotas.
If you want to protect this application, consider obtaining a server quota.
Otherwise, do not enable Application backup for this machine.