@SJS66 - This same question came up yesterday. The reality is, no matter how well we all draft in CAD, there will ALWAYS be gaps and overlaps due to the way SketchUp converts vector arcs to segments. This ‘CCdesignbase’ plan in particular is challenging due to the many curves and tangent lines.
See this post here: Edge tools not closing gaps - #7 by eric-s
The extensions reviewed in the course will solve the gaps issue. Let me know if you experience any other problems.