Anyone having issues with users being able to view activities in the in Activity timeline after the Winter 27 release?

Hi Barb, 

I couldn't find a confirmed public Known Issue tied specifically to Winter '27 for this yet, so this may be new/unreported so far. A few things worth checking first, since these are the most common causes of activities suddenly disappearing after a release: 

1. Setup > Record Page Settings — check if "Default Activities View" got reset to "Related List" instead of "Activity Timeline" (or vice versa) for affected users/profiles. Releases sometimes reset this default. 

2. Check if it's a permissions/FLS issue on Task/Event fields specifically introduced by a release-related metadata change, rather than the timeline component itself. 

3. Ask affected users to try Personalize view (gear icon on the Activity component) to reset their individual view — a stale personalized setting can also break post-release. 

Reference:

If none of that resolves it and you can reproduce it consistently, worth opening a case and referencing Winter '27 explicitly — if others in this group hit it too, it'll likely get logged as a Known Issue soon.