Reason

The Server Maintenance Folder, which is automatically created during the first launch of PowerFolder Server, may not be accessible by the server anymore. This can have two reasons:

The permissions on the Server Maintenance Folder doesn't allow the user who runs PowerFolder Server to read/write in this directory.
The location of the Server Maintenance Folder has been changed and the change has not been applied to the Server Configuration File.
The location where the Server Maintenance Folder resides is temporarily not accessible, e.g. because it is located on a network drive which has been disconnected temporarily.

In all of the above mentioned cases PowerFolder Server may try to (re)create a new Server Maintenance Folder, because the old one can not be found. Since also the license keys for user devices are stored there, the server will not find the current device licenses.

Solution

Find for the location of the Server Maintenance Folder in the Server Configuration File

Please check the Server Configuration File. There should be an entry like the one below:

plugin.server.maintenancefolderid=[<folder_id>]

Please write down the folder_id, since you will need it in the next step.

Search for the folder_id mentioned in that entry. You will find some entries entries which look like the ones below:

f.<folder_identifier>.archive=FULL_BACKUP
f.<folder_identifier>.commit-dir=
f.<folder_identifier>.dir=<path_to_server_maintenance_folder>
f.<folder_identifier>.dlscript=
f.<folder_identifier>.id=[3mfJYiYMzWMzWEJgLLik]
f.<folder_identifier>.name=server_maintenance
f.<folder_identifier>.preview=false
f.<folder_identifier>.sync-patterns=true
f.<folder_identifier>.syncprofile=true,true,true,true,1,false,12,1,m,Auto sync,true
f.<folder_identifier>.versions=5

Check for possible problems with the location of the Server Maintenance Folder

Please head to the path mentioned in the f.<folder_identifier>.dir variable and...

check if that directory exists. If it doesn't exist please check on level above in the directory structure if it has another name. If it has been renamed, please stop the service, change the value of the f.<folder_identifier>.dir in the Server Configuration File and start the service again.
check if it is accessible to the user account running PowerFolder Server. If it is not, please apply the correct rights on that folder and restart the service afterwards.
check if a second Server Maintenance Folder exists in the directory one level above. This might be the original one, which PowerFolder Server couldn't temporarily find and therefore created a new one. If a new one has been created, please stop the service, change the value of the f.<folder_identifier>.dir in the Server Configuration File to the path of the original location and start the service again.
If your Server Maintenance Folder resides on a network path, we recommend to stop the service, move it to the local storage, change the path in the Server Configuration File as described above and start the service afterwards. Since network storage might become unavailable temporarily, there is always a chance that the server might not find it and tries to recreate it.