I would like to follow up on a question I posted quite some time ago.
After some unsuccessful attempts to find out why my TB KML is not showing in Google Earth I gave up the hope that my TB will show its travels in Google Earth (GE) - Ever!
However, god knows why, one day I decided to download and edit the KML of the TB. I also read (again) the error I got from Google Earth (GE) GE reported while the KML was loaded. Error listed the line and column where GE supposedly decided that the TBs KML is not OK for it. Than I looked what is at that position in the KML itself.
I found that Google Earth didn't load a KML due to a ' character (apostrophe used in words like "I'll" & "didn't" )!!!
I remember that I wrote a TB description in the Word and than I copied/pasted prepared text to the Geocache TB site. After this copy & paste actions, and save of the TB descriptions, GE rejected all ' characters. It looks like it did not like those "strange ' characters" within KML TB descriptions.
I had to correct all apostrophes (') in the TB description. Strangely it was enough to replace them with "the same" (') character directly on the Geocaching TB site (so on the page, which you get when you EDIT the TB description). When I did that KML was happily accepted by GE. Hurray! TB shows its KML in GE!
It looks like during the copy & paste action from Word to WWW Geocache TB edit site, something happened to the ' character and changed it to something that is recognized as ERROR within KML by GE.
I hope this experience will help other to avoid the same mistake!