First, confirm that the user has read and write access to the temporary scanning directory configured in the registry. If only MHT documents are not displayed, then the Internet Explorer security settings on the scanning workstation may be too strict to display MHT documents.
The specific settings needed to allow navigation vary depending on the content of the MHT document. To troubleshoot the issue, open the MHT document externally from OnBase using Internet Explorer. If Internet Explorer returns an error message, adjust the security settings as indicated by the message.