Export fails because a Pleo verification series was added to the wrong financial year in Fortnox
In Fortnox, double-check that you're in the correct accounting year:
Next, create a new verification series for Pleo. To do so:
Click Settings (Inställningar).
Click Bookkeeping (Bokföring).
Verification series (Verifikationsserier).
Add a Pleo (P) series and tick the box in the manual column (Manuell Kontering).