If you have followed all five solutions and still face the error, your Windows installation may have deeper corruption. Run sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth before contacting PTC Technical Support.
For air-gapped systems, you must manually export certificates from an internet-connected machine and import them.
For further assistance, users are encouraged to open a support ticket via the My Kepware portal download links
Select the signature in the list and click > View Certificate . Install to Root Store: