The cause:
The selected category in Pleo reflects a Fortnox account where “transaction info” is mandatory. "Transaction info" in Fortnox refers to notes on Pleo expenses.
The solution:
Add a note to the affected Pleo expense(s).
Or
In Fortnox, turn off the mandatory stipulation for notes:
Click "Register".
Click on chart of accounts (Kontoplan).
Click on the relevant account.
Make transaction info "allowed" instead of “mandatory”:
Click save (spara).