If you are using the System-wide control on macOS 10.13 and below, we've identified a bug that produces this error on installation of the Volume Limiter Lock utility. This bug was fixed in v1.0.5 (released in January 2020)
In order to resolve this, please do the following:
1. Download and install the latest Volume Limiter Lock utility (even if you are a website user!)
2. Perform the uninstall (Daemon only)
3. Perform the install
4. If you are using the website version, please delete the Volume Limiter Lock utility.
This should resolve all issues for both website and App Store users. If this isn't working, or is unrelated to your issue, please submit a ticket.