Adobe InDesign 2026 rejects CC2026 SDK sample plug-ins on macOS

I am testing native C++ InDesign plug-ins on macOS using the Adobe InDesign CC2026 SDK.

Problem:
InDesign 2026 on macOS rejects both my custom plug-in and Adobe’s own unmodified BasicDialog sample plug-in with the startup message:

“Adobe InDesign does not recognize [plugin name] as a valid plug-in.”

Environment:

• InDesign 2026

• CC2026 SDK

• macOS

• Xcode 15.x

• Tested on multiple Macs/users with same result

Important finding:
Even Adobe’s own BasicDialog sample from the CC2026 SDK fails to load, so this does not appear to be specific to my plug-in code.

What I already verified:

• Mach-O Type = Bundle

• arm64 architecture enabled

• Bundle structure exists correctly:

  • *.InDesignPlugin/Contents/Info.plist

  • *.InDesignPlugin/Contents/MacOS/[binary]

• Info.plist executable name matches binary name

• Plugin is code signed

• codesign --verify --deep --strict reports valid

• spctl and quarantine/security/privacy checks were tested

• Same rejection occurs on multiple Macs

• Security & Privacy blocking does NOT appear to be the issue

Question:
Has anyone successfully loaded CC2026 SDK sample plug-ins on macOS with InDesign 2026?

Is there:

• a new signing/notarization requirement,

• a required Xcode/macOS combination,

• a known SDK issue,

• or additional bundle/build settings required for CC2026 Mac plug-ins? Thanks.