There could be several reasons why this happens, and the message displayed in your chat window will help diagnose the issue.

If you do not see any contextual message in the chat window ensure you have 'Invalid price warnings' enabled in your TSM settings (i.e the option is toggled off):

Common reasons that cause 'item/group is invalid':

1. You have no pricing data. Ensure you have the TSM Desktop Application installed and configured correctly.
   • Related Article: How do I setup the TSM Desktop Application?
2. Your normal or maximum price is lower than your minimum price. Ensure that your normal and maximum price is higher than your minimum price.
   • Your normal price is used when there is no competition to undercut between your minimum and maximum price. Your normal price cannot be lower than your minimum price.
3. Your minimum, normal, or maximum price is invalid. Ensure your custom string returns a value, both in general and for the item you are specifically posting.

Other reasons that cause 'item/group is invalid':

1. Your undercut amount is invalid. Ensure the undercut amount returns a valid value.
2. Your keep quantity is invalid. Ensure the keep quantity returns a valid value.
3. Your max expires is invalid. Ensure the max expires returns a valid value.
4. Your stack size is invalid. Ensure the stack size returns a valid value for the item being posted.