I am referring to these columns when creating an add row action in Power Automate:

You don’t put the dynamic value of the related entity in there by itself. Instead you need a format like /entityset (keys)

If you don’t you will probably get an error along the lines of Resource not found for the segment

I renamed my account entity to Customer so for me it says Customer (Customers) but for you it may say Account (Accounts)

Custom entities will have your publisher name in front of it. I have two custom entity examples below:

  • Customer (Customers)
    • /accounts(GUID)
  • Currency (Currencies)
    • /transactioncurrencies(GUID)
  • Design Number (Designs)
    • /publisher_designs(GUID)
  • Design Request (Design Requests)
    • /publisher_designrequests(GUID)
  • Lead (Leads)
    • /leads(GUID)
  • Opportunity (Opportunities)
    • /opportunities(GUID)
  • Orders
    • /salesorders(GUID)
  • Owner (Owners)
    • /systemusers(GUID)
  • Price List (Price Lists)
    • /pricelevels(GUID)
  • Product (Products)
    • /products(GUID)
  • Quote (Quotes)
    • /quotes(GUID)
  • Unit (Units)
    • /uoms(GUID)
  • Users (Users)
    • /systemusers(GUID)

References:

https://powerusers.microsoft.com/t5/Building-Flows/Resource-not-found-for-the-segment-Custom-Entity/td-p/792802  

https://debajmecrm.com/resource-not-found-for-segment-error-in-power-automate-microsoft-flow/ 

https://powerusers.microsoft.com/t5/Power-Automate-Community-Blog/Resource-not-found-for-the-segment-issue-in-Power-Automate/ba-p/552837