alas, the enterprise version of Windows 10 LTSB and Windows Server 2019 have only V1809 and are updated every 4 years. Microsoft policy. At the same time, as we know, your application has not been updated for a couple of years. So this error is caused by Start10 and not Windows. We are waiting for suggestions on how you can solve this problem ? We can provide remote access to demonstrate the error
Why do you believe our software has not been updated in a couple of years?
The version you are using is six months old but v1.96 was released today which I would recommend trying as a first step.
With regards to your issue, are you sure both admins have the exact same permissions? It very much sounds like the user does not have permission to shut the pc down.
Did this previously work for you, or have you only recently installed Start10 on this machine?