Ah i see, thanks for the advice, yes i went through net properties and other possible solutions and done my head in changing this and that , basically button pushing ! several cups of coffee later , Until i thought about it and went back to the beginning ie the schematic and thought, how does it know what to connect and where , answer , the button i had not pushed yet RATLINES !!!, so i went to the bottom board layer and connected the two points it refused to connect up and linked them with a ratline and bingo now it makes a trace between the two points. Somehow in my re-jigging of the component placements i erased traces and these did not show the original ratlines and hence when trying to re-install a net trace the points are clueless as to where to connect because there is no ratline.
Anyhow thats how i figure it works , strange because it is not always the case ?.
So to re-install a net trace connection that is being a pain my solution is to goto ratline button, choose, and re-connect the two points . It worked for me.
Thanks for all the contributions of help, i,m on a learning curve here LOL !!!. Cant imagine what KiCad or Eagle is like to learn i have seen mixed reviews about many design softwares but i like Diptrace.