OneNote 16.109.3 + macOS 26.5.1 → WebContent sandbox failure causes Tags pane to render blank

Question

OneNote 16.109.3 + macOS 26.5.1 → WebContent sandbox failure causes Tags pane to render blank

Alice Friedemann 0

The Tags pane (custom tags panel) renders completely white and is unusable. The issue appears to be a WebKit/WebContent sandbox restriction introduced in macOS 26 (Tahoe).

Relevant log errors:

WebContent[8929] Connection init failed at lookup with error 159 - Sandbox restriction

WebContent[8929] The sandbox in this process does not allow access to RunningBoard

ProcessAssertion::acquireSync Failed to acquire RBS assertion 'WebProcess NearSuspended Assertion'

Environment:

• OneNote version: 16.109.3 (26053122)

• macOS version: 26.5.1 (25F80)

Anyone has any workaround or fixes to this issue? I do not want to use the web version.

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1 answer

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Answer 1

Kai-H 26,385 Microsoft External Staff Moderator

Hi, Alice Friedemann

This looks less like a normal notebook or sync problem and more like the custom tag pane failing to load inside OneNote’s embedded web component on macOS.

Here are some suggestions you can try:

First, check OneNote’s connected-experiences setting. In OneNote, open Preferences, then Privacy, and make sure optional connected experiences are enabled. It is recommended that this setting matters because custom tags appear to rely on OneDrive/cloud-backed behavior, and disabling it can affect the custom tag UI.

If this is a work or school Mac, also check whether it is managed by MDM, endpoint security, VPN, or privacy-control software. The RunningBoard/sandbox messages point to macOS blocking the WebContent process, so a company security profile may be involved. Testing once in macOS Safe Mode, or in a fresh local macOS user account, can help confirm whether OneNote itself is broken or something running in the background is interfering.

As a temporary non-web workaround, create or edit the custom tags from another OneNote desktop client, such as Windows, then let the notebook fully sync back to the Mac. If the Mac can apply existing tags but cannot open the Create Tag pane, this avoids the broken pane until Microsoft fixes the Mac build. Custom tags are still shown as a supported OneNote for Mac feature, so if these checks fail, I would treat it as a product regression rather than keep reinstalling repeatedly.

Thank you for your patience in reading, I hope this information has been helpful to you.

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Kai-H 26,385 Reputation points Microsoft External Staff Moderator

2026-06-08T07:06:23.41+00:00

Hi, Alice Friedemann

It has been a while and I am writing to see how things are going with this issue.

Have you had a chance to check the replies provided?

Any update would be appreciated.
Alice Friedemann 0 Reputation points

2026-06-09T00:26:28.76+00:00

Hi @Kai-H unfortunately neither of you suggestions worked, safe mode nor fresh user. Thanks for your time and consideration though.
Kai-H 26,385 Reputation points Microsoft External Staff Moderator

2026-06-09T06:12:55.42+00:00

Hi, Alice Friedemann

Thanks for checking. Since Safe Mode and a fresh macOS user did not change anything, this is looking more like a OneNote/macOS Tahoe compatibility problem than a damaged local profile. The Create New Tag pane is still documented as a supported OneNote for Mac feature, so a blank pane is not expected behavior.

First, if you can get the old build, it is recommended that you roll back to OneNote 16.99 for now. There are reports where custom tags worked in 16.99 but stopped in later 16.105/16.106 builds. After installing the older build, turn off automatic updates in Microsoft AutoUpdate so OneNote does not immediately update back to the affected version.

Second, try a completely different network, ideally a mobile hotspot, with VPN, proxy, private relay, content filters, and security filtering turned off. The tag pane appears to load web-based content inside the app, so if that web component cannot load properly, the pane may stay blank.

If neither works, I would report it from OneNote through Help, Feedback, and include the exact OneNote build, macOS build, and the WebContent sandbox errors. At that point, repeated reinstalling is unlikely to help.
Kai-H 26,385 Reputation points Microsoft External Staff Moderator

2026-06-15T06:32:14.4833333+00:00

Hi, Alice Friedemann

Is there any update from you?

If yes, please feel free to let me know.