The floor disapear

Thank you for reading my post.
I have some trouble with the floor of my project because it’s not anymore represented.
I Have try many way to represent it agin but nothing work. Must I start my project again from scratch?

Please attach the model or at the very least a screen shot so we have some idea what to tell you.

Seventh icon from the left at the top of the message box is the upload button.

Thank you for your answer and the attachment advice. There is my flat.

The footprint of all the walls isn’ t a close loop of edges.

(provided that nothing is grouped yet) Draw edges across the door openings at floor level (horizontal).
Once these few new edges plus the inner wall edges form a close loop SketchUp can create a face.
You may need to also draw edges (temporarily) across inside door openings.

Thank you, a lot of work but its working…

Another method that works well for me. First group the entire floor model so that the next geometry will not “stick” to it. Then with the line tool trace around top outside edge of the walls making a closed loop. A surface should be formed. Using the Push/Pull tool, pull up the surface the depth of the floor system. Group this. Then use the move tool to grab an upper corner of the new floor and move it down to the bottom of the wall. You now have your floor system.

Or draw a rectangle and remove the bits you don’t want.