Hi,
Best practice is frequently uploading the Units of Measurement from an SAP Source System (usually ECC) where the transaction data is processed. It should not be possible to have transaction data with Units of Measurement which does not exist.
Please run the upload (t/code RSA1 > Source Systems > SAP ECC: context menu Transfer Global Settings). Check afterwards t/code CUNI. If the missing Units of Measurement are available, run the activation once again.
Note: the Transfer of Global Settings should be executed on a daily basis using a Process Chain or background job. Please check if that is the case.
Best regards,
Sander