I am trying to render and burn a Blu-ray using the Markers created in Movie Studio Platinum 12. I am following the steps outlined in Steve's book Guide to Movie Studio Platinum 12 on page 236 and I want to take the video into DVD Architect Studio. Here is what I did, starting at step 4 Click on Make Movie button at the top of the program's interface, or select Make Movie from the project menu. On the first Make Movie dialog window that opens, select the option to burn to a DVD or Blu-ray Disc. Click next. On the next Make a Movie dialog window, select either the DVD with menus or Blu-ray disc with menus option. This is where the issue arises, the option to select Blu-ray with menus was grayed and non-select-able. The only options were DVD with menus, or Burn to Blu-ray. What am I missing? Does it sound like I missed any steps? Please advise me so I can use DVD architect, I really thing DVD architect could make a good DVD or Blu-ray much better if I could get it figured out.

If you're working with 5.1 surround projects, read this from the MSP 12 Release notes.

"The Tools > Burn Disc > Blu-ray Disc with Menus command is not available when working with 5.1 surround projects. You can use Tools > Burn Disc > Blu-ray Disc to burn a 5.1 surround project from the timeline. If you want to use DVD Architect Studio to author a Blu-ray Disc with menus, please use the Audio tab in the Vegas Movie Studio Project Properties dialog to set your project's Master bus mode to Stereo".

These burning problems may sometimes be solved by toggling the "Use legacy disc drivers" option in Options > Preferences > Burning. This option is in the later builds of DVD A Studio 5. See also the similar option in MSP 12 Preferences > CD Settings. Worth a try.

Thanks VKmast, I bet you are right about this, because I used 5.1 surround. Interesting that this would cause me to lose functionality else where in the program. My guess is most projects would sound fine in the stereo mode anyway. Is that how you see it?

More audio-oriented users do complain about this, but as noted you are only able to "burn a Blu-Ray disc with 5.1 Surround Sound directly from the timeline" (PCM audio) with MSPs. For BDs with 5.1 surround and menus you need to use Vegas Pro and DVD Architect Pro.
Here's the Vegas Knowledgebase document on this.
https://www.custcenter.com/app/answers/detail/a_id/5030