Hi Miro1,
I appreciate the steps you've made to resolve the error.
You may have incorrectly set the unit of measure for the product. You can verify this by going to the Items & Inventory page.
Let me walk you through the steps:
- From the Edit menu, then select Preferences.
- Select Items & Inventory.
- Go to the Company Preferences tab.
- Check the Unit of Measure section.
Also, can you share with me the exact error message you get when atttempting to add an alternative vendor for an item? So, I can provide the correct solution based on the error.
Feel free to check this article that has information about measure of unit: Use single and multiple units of measure for items.
You can always visit us here again if you have other questions. We'll be happy to help anytime.
