Are you asking about the blue highlighted edge, or the grey construction line?
Could you attach your file?
Hello Nicole,..the "blue" is showing a gap which is/was too wide (they do not touch or not within a tolerance gap for them to Knit or close/join/merge..?
So, without seeing the file,.. I would suggest you either try to simply apply a Face Fillet on the edge to close the gap... or, try to go back to the edge/gaps of the two surfaces and Extend/Trim them?
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