If someone can't see a feed, it's usually one of two things.
1. They're not at the feed's location
On the web, go to People and click the person's name.
On the Information tab, find Location & roles.
Add the missing location under Locations.
Click Save changes.
If their locations come from your rota or HR system, change it there instead; All Gravy picks it up on the next sync.
2. The feed needs them added by hand
Some feeds, such as a managers' feed, are only for chosen people.
Go to Feed and hover over the feed in the list.
Click the pencil.
Under the audience, click Manually adjust audience.
Search for the person and click Include, then Save.
Click Save again on the audience to keep the change.
Only Admins and Editors can change a feed.