what should i do when my sketchup file have an error whit this message "this dose not apear to be a sketchup mode
You could share the .skp file with us so we can see if there’s something that can be fixed. Did you try renaming the .skb backup file to .skp to see if it would open?
Where are you saving the SketchUp file while working on it?
Your forum profile says you are using a Classic license for SketchUp 2023. Does that mean it is a cr acked version?