Thank you for posting your question. Please check this out PowerShell Script to Update New Client-Side Certificates for Patch for Windows Servers 9.3 and try updating the certificates on one of the clients as it sounds like the client is missing system certificates. If that does not work, please create a case at support.ivanti.com and we can send a Microsoft tool to update your system certificates as well as other Microsoft documentation that will update the system certificates.
Thanks, attempted and failed validation still. Will open support case.
For others reviewing this, I was able to resolve the file validation error by opening a support case and being given some cert update tools which refreshed the Adobe root certs on this particular server. Following that, a deployment, and a rescan, the server reported back with no missing patches.