On the below link you can find a list of Units of Measures in PEPPOL, so please check in BC thats your mapping between your setup BC match the PEPPOL codes
Here you can see how its done from Danish GREEN to PEPPOL RED
Belkow Link to the offcial PEPPOL Units of Measure list
Peppol BIS Billing 3.0 | Rules
This will be the error if not setup is correct
{"message":"Invalid Document","errors":[{"context":"/Invoice[1]/InvoiceLine[1]/InvoicedQuantity[1]","pattern":"","text":"[BR-CL-23] [BR-CL-23]-Unit code MUST be coded according to the UN/ECE Recommendation 20 with\n Rec 21 extension","isWarning":false},{"context":"/Invoice[1]/InvoiceLine[1]/Price[1]/BaseQuantity[1]","pattern":"","text":"[BR-CL-23] [BR-CL-23]-Unit code MUST be coded according to the UN/ECE Recommendation 20 with\n Rec 21 extension","isWarning":false}]}'