In Dimensions, for each relevant customer, the terms window needs to have custom ticked and when you click Due Days, one of the following options needs to be selected before the information in the Terms field can be synched:
End of following month
Day of following month
If the customer account was set to different options to listed above and imported into FactoryMaster, the manual payment terms info will not import. The terms options have to be set like above for the customer account in Dimensions and then the imported customer account needs to be set to manual payment terms from customer maintenance in FactoryMaster, for the manual payment terms information to be imported.