No problem, I will take the repro steps you have provided to see if I can get the issue to occur on my end. I will report back once I have completed my testing with any new information or troubleshooting suggestions.
Edit: To verify this is a C++ template project correct? As you description alludes to programming logic
I have exactly the same problem.
Migrating the project from 4.8.3 to 4.9, all call to DrawMaterialSimple(), working before, do not draw anymore. In viewport, new viewport or Standalone game.
I was able to confirm the issue in 4.9 as you are reporting. I have gone ahead and entered a bug report for this issue (UE-20792).
When a fix for this issue has been implemented it will be added to the release notes of an upcoming hotfix or full release. You can find the Release Notes on our Documentation or the Forums under the Announcements and Releases section.
As mentioned below in my answer for this issue, I have entered a bug for this issue. This is a far as I can go until the developers get a fix implemented into an upcoming release or hotfix.