InfoPath Filler 2013: How to resolve ‘This form cannot be opened because it requires the domain permission level…’ error

I have an InfoPath form stored on a network drive that submits to a SQL database. A few years ago, when updating from 2010 to 2013, users started receiving the following error when attempting to open the form in filler:

“InfoPath Error: Forms that require the domain permission level contain features that access information on a network, such as data connections, linked images, and code.”

"InfoPath Error: Forms that require the domain permission level contain features that access information on a network, such as data connections, linked images, and code."

Over the years, the issue has been sporadic and we haven’t been able to pinpoint the cause or a permanent fix. We’ve scoured the forums, and have attempted many recommended fixes, but none seem to fully resolve the issue. Does anyone have any recommendations? Here’s what we’ve tried so far:

  1. Reviewed SQL database and network drive permissions.
  2. Updated InfoPath form Security Level from “Automatic” to “Domain” permissions.
  3. Attempted to update Security Level to “Full Trust” (but disabled by Admins).
  4. Digitally signed the form template with a valid user certificate.
  5. Published form to a different network path under a different name.
  6. Published to a SharePoint site.
  7. Updated form compatability settings from InfoPath 2010 Filler Form to InfoPath Filler Form.
  8. Updated form versioning settings to “Automatically update template” and “Automatically upgrade existing forms”.
  9. Cleared InfoPath cache using RUN command: InfoPath /cache clearall
  10. Updated Trust Center Settings by deselecting “Check Microsoft Office documents that are from or link to suspicious Web Sites.”
  11. Full review of form to ensure any rules used Fully Qualified Path, instead of network drive shortcut.
  12. Instructed form users to open form in Design mode, then “Preview” the form.

The only one that has worked, has been (item 12) for users to open in Design, then click preview. We do not want our users opening the form in Design mode. Any suggestions?