Hi JeanNY! I was meant to write sooner but my broadband was down; it was fixed yesterday. Anyway, I was thinking about your query & there are some possibilities after consulting the Diamond Dowsing Manual:
(1) If you have just got the course pack it might be that you need time to get used to the Dowsing Rods.
(2) Try doing the "tubes of light" meditation everytime you want to use the rods...it takes 2 minutes. For example even in a particular day no matter how many questions you want ask you only need to do this once. And if you're going to use it again the next day do the meditation again & so forth.
(3) Another possibility is that you may not be in a relaxed state...if you read the manual it states that you need to "let go". That could help as well.
After more time & practice you'll be able to use the rods effectively & also it will become attuned to you. It was like this with me & a few others I know who use this.
Hope this helps.
GUILLAUME.