Refreshing and limits
Nightly runs, the manual refresh and its cooldown, and how many profiles you can have.
Nightly runs
Profiles are re-run automatically as part of the nightly pipeline, after the sources have been synced. That is why new matches are there in the morning and why the daily email arrives when it does, see Email alerts and the daily digest.
You do not need to refresh anything to receive new tenders. The manual refresh exists for a different reason.
Manual refresh
Refresh manually after you changed the profile and want to see the effect immediately. A manual refresh is limited to once per profile per 24 hours, because a run is expensive.
One exception: if you edited the definition and the list is therefore out of date, the refresh is allowed even inside the cooldown. That is the case the "your list is older than the profile" banner points at.
On top of the per-profile cooldown there is a daily run budget per organization, so a large team cannot exhaust the pipeline by refreshing everything at once.
Profile limits
The plan includes three active search profiles per organization; more are available as add-ons, and the dialog that appears when you create one too many offers exactly that. See Plans, trial and limits.
Archiving a profile you no longer need frees a slot. Archiving is reversible in the sense that nothing is deleted immediately, but the list stops being updated.
When a run produces nothing
A run with zero new matches is a normal result, not an error: it means nothing was published that fits. If several runs in a row produce nothing and you expect otherwise, check the geographic gate first, it is the filter that removes the most.