Pants and Coat For The Toddler Grandson - a night of serging

I spent the evening serging all the possible seams on my DGS's Christmas gift.  It only took me 1 1/2 hours.  However I spent a previous 45 minutes trying to get my serger threaded correctly.  I just had a looper replaced, and the repair person kindly left their thread in place.  I knotted the new thread to their thread, but it just wouldn't work right.  I couldn't see where my problem was.  Finally, I saw the problem, and the rest of the evening sent smoothly.