Line Item Selector cannot be edited if any live receipt tag is associated with it. So when the Line Item Selector is edited the error message is displayed along with the Qualification criteria name which is associated with it and has live receipt tags.
Then go to the Qualification Criteria section (Settings > Qualification Criteria)
Search the Qualification criteria by their name.
The Qualification criteria will be filtered. The receipt tag will be displayed in the blue block.
Search this receipt tag in the Receipt tag section (Guests > Receipt Tag)
Note: Please refer to the article How do I deactivate a Receipt Tag? on how to deactivate the live receipt tag.
If further assistance is required, submit a ticket to Punchh Support. (For help submitting a ticket, click here)