Two different questions get asked here: why your own entry is not in the public entry list, and why other people's entries are not visible. They have different answers.
Why your own entry may not appear in the public entry list
An entry shows on a competition's entries page only when all of these are true.
- It has been approved. Entries start as received and unreviewed, and an unreviewed entry is not listed. Rejected entries are not listed either. An entry marked Perfect counts as approved here and is listed.
- It has not been withdrawn. Withdrawing archives the entry, and archived entries are left out.
- It has a project, journal, or publication attached. An entry with nothing connected has nothing to display, so no card is drawn for it.
- The attached work is viewable. For a project entry that means the project has a published version. If it was never published, or was unpublished, the card disappears from the list even though the entry itself is fine. Publish it and the card comes back.
So an entry that is still awaiting review and not showing publicly is normal and expected, not a fault. Approval is what makes it public. If your entry is approved and the connected project is published but it still does not appear, that is worth reporting.
Why other entries are not visible
If a competition shows only your entry, or very few, that does not mean you are the only participant.
The Entries link on a competition appears once the competition's shortlist date has passed. If the competition has no shortlist date, its results date is used instead. Before that the link is not shown, which keeps judging fair during the submission window. That runs off the competition's own dates for almost every competition. A small number carry an override that opens the Entries list earlier, so if you can see entries on one competition and not on another at the same stage, that is why rather than anything going wrong. On a narrow screen the Entries tab stays hidden even where the override applies, so check on a desktop browser before concluding it is missing.
Once the link appears, entries are grouped by award: Winner, Runner-up, Shortlisted and so on, with everything else under Other Entries. The Leaderboard link appears on the same schedule.

How to check your own entries
Your competitions page at uni.xyz/profile/edit/{your-username}/competitions shows the real review status of every entry you have, and the entry's Analytics page gives the detail for one entry.
If something still looks wrong, contact the UNI team with the competition name and which entry you mean.