Surface is not building when connecting the end and start of a road

When I am trying to connect the start and end of a road to have a closed surface the surface area e.g. grass is not appearing. The surface is not build correctly.

[Shahzeb]

I get the error:

Answer 1

[Kiven]

Please paste your code. And what is the surface of your work?

[Shahzeb]

There is no source code. I am just building it with the interface