See PHI1351. After recent changes, build plans may be marked non-restartable.

This also means that Restart All Builds on the Buildable does not restart them. While this behavior is correct, the label and messaging are misleading. Better would be:

• In the confirmation dialog, show a list of affected builds and clearly mark which ones will restart and which ones will not (and why).
• Probably, rename the actual action to just "Restart Builds".