That means that lightning payment did not complete. Happens when recepient issued hodl invoice or when payment gets stuck while routing.
Wallet checks with mint on each start and around every 1 min while in use on state of pending payments, so it should resolve, however can take some time.

If not failed/settled today, dm me the audit trail, I'll check on the lightning node directly. 

 I tried to get a failed payment with that zap but it succeeded 😂 so next time it happens I'll leave it pending if I can. 

 So when this happens, the payment doesn't become pending, it just stays as an Error:

https://i.nostr.build/u02AjCDqx0VAbkit.jpg

Dming the audit trail.