If the situation happened when there are no users with Administrator Role remaining in the system then nobody will be able to configure ActivityTimeline.
...
The zip package contains README.txt file and admin-access-restore.jar file that can assign Administrator role to a specified user.
INSTRUCTIONS:
1. Stop ActivityTimeline (launch "<AT_INSTALLED_FOLDER>/activitytimeline/bin/shutdown.sh" (Linux) or "<AT_INSTALLED_FOLDER>\activitytimeline\bin\shutdown.bat" (Windows))
2. Backup "atdb" folder (usually activitytimeline/bin/atdb).
3. Place this jar file into "atdb" folder (usually activitytimeline/bin/atdb).
4. Launch this jar file using the following command:
java -jar admin-access-restore.jar USERNAME add_user_if_missing
USERNAME should be replaced with a real username of user who should restore an Administrator role.
5. Start ActivityTimeline.
External database mode
Use the following link to download the tool: https://activitytimeline.com/tools/admin-access-restore-v3.zip
The zip package admin-access-restore.jar file that can assign Administrator role to a specified user.
INSTRUCTIONS:
1. Stop ActivityTimeline (launch "<AT_INSTALLED_FOLDER>/activitytimeline/bin/shutdown.sh" (Linux) or "<AT_INSTALLED_FOLDER>\activitytimeline\bin\shutdown.bat" (Windows))
2. Unzip downloaded admin-access-restore-v2v3.zip package into <HOME_FOLDER>
3. Copy '<AT_INSTALLED_PATH>/activitytimeline/webapps/ROOT/WEB-INF/classes/configuration.properties' file into <HOME_FOLDER>
4. Open <HOME_FOLDER> and launch this jar file using the following command:
java -jar admin-access-restore.jar USERNAME add_user_if_missing
USERNAME should be replaced with a real username of user who should restore an Administrator role.
5. Start ActivityTimeline....