Notifications are not arriving

Work through these in order.

Check the obvious one first

Open your notification settings and confirm the category is on. Arrivals, departures, low battery, journeys and pings are all separate, so it is easy to have turned off more than you meant to.

Check you have not muted the person

Muting one person silently stops their arrivals and departures for you alone, and it is easy to forget. See Muting someone.

Check the place is not quiet

A quiet place never announces anyone. If one person seems to arrive silently everywhere, check your settings; if everyone is silent at one location, check the place. See Quiet places.

Check your phone's own settings

Circl needs notification permission at the system level. If it was declined when you first installed, the app cannot ask again and nothing will arrive regardless of what is set inside Circl.

If nothing arrives at all, from anyone

That is different from missing some, and it usually means permission was never granted or was later revoked. Check your phone's settings for Circl, then reopen the app.