I have added a piece of pipe to my model it is #15 to join to a bending pipe #10 and pipe #29 after but #15 will not line up to #10 and #29 is joining to #10 I dont know why this is please help

The element going into the bend must be followed immediately by the element exiting the bend. This means, when you use [PgDn] to view the spreadsheets for each element, these two elements are back-to-back.