Hi Lucas,
i would suggest to you if it is really issue is coming for number range then plz goto OBA7 n check for RV document type for invoice n as well as number range , then go to FBN1 and find out the same number ranger n write down which number is current then please again try to reverse the invoice n check in FBN1 number range has been pick next one if it so .
then it means your number range has been terminated so this case you need to change your number from status in FBN1