<<Sympton>>
STAgentUpdater.log
WinTrustVerifier.cpp:195 Certificate verification failed with error : -2146762748
<<Reason>>
The OS is unable to verify the digital signature. The specific error is -2146762748 which is a Mircosoft error that translates to "The subject is not trusted for the specified action"
<<Solution>>
1) Update the Root Certificate on the client machine. You can update it manually or run a scan with Security Tools enabled against it. It's going to be MSRC-001 or MSRC-002.
2) It's possible the System Account (used to run the agent services) is having issues on the machine. You could attempt to run the agent services as a domain account as a test.