Hi. That was my awful blog.
I'm glad to see you got that rot-file working. It took me a few errors to get it working myself.
The most likely problem is that you need at least to lines for each plateid. One for the initial time and one for the final time.
Positions are interpolated, but gplates can't extrapolate. Neat thing is that gplates will automagically create new lines when you move plates around.
I tried to be pretty thorough(boring, longwinded, dull as slow-moving brown mud), but if I missed anything, questions could help.