A recent Microsoft PowerPoint update has introduced a bug affecting Macabacus users. This is a M365 bug, not a problem with Macabacus — it can be reproduced natively in PowerPoint with no Macabacus add-in involved, and affects any operation that copies a slide or shape out of a read-only presentation.
We have escalated to Microsoft and are awaiting a fix.
What’s Happening
The update changed how PowerPoint handles presentations opened in read-only mode, and now blocks copying any slide or shape out of a read-only file. Macabacus opens library files in read-only mode by design when inserting content, so any feature that copies a slide or shape out of a library is affected, including inserting tombstones, shapes, and slides. Library content that doesn’t rely on copying from an underlying .pptx (e.g., images) are unaffected.
If you’re affected, you’ll see the error: “Shape (unknown member): Invalid request. Presentation cannot be modified.”
This occurs with local files as well as files stored on OneDrive, SharePoint, and other locations — it is not specific to any cloud storage or co-authoring configuration.
Affected Versions
Current Channel 2606 is affected (PowerPoint Build 20131.20090, released June 25, 2026). Several Current Channel (Preview) builds are also affected.
The prior release, 2605, is not affected (PowerPoint Build 20026.20182, released June 16, 2026).
To check your build, go to File > Account > About PowerPoint.
What you can do now
For IT administrators, there are two interim options:
Roll back to the prior build. Rolling affected machines back to Current Channel 2605 should restore functionality; we have not been able to reproduce the issue on that build.
Suspend M365 updates. Machines still on 2605 or earlier are unaffected. Pausing or deferring M365 updates keeps them on a known-good build until Microsoft releases a fix.
What we’re doing
We’ve reported this to Microsoft and are pushing for a prompt fix. In parallel, we’re testing a workaround on the Macabacus side that may restore functionality while Microsoft addresses the root cause.
For full technical detail, reproduction steps, and ongoing updates, see our Known Issues article.