There are three possible problems:
1. The ID was defective when you bought it.
2. The ID was OK, but is now no longer working.
3. You are not handling it right.
Echoing dat8962, the possible remedies are:
a. Return the ID and get a refund or a new one.
b. Buy a new one.
c. Re-treat the ID. See
http://www.talkmagic.co.uk/sutra186081.php .
d. Try different ways of handling it. Try holding it nearer the ends, or nearer the middle. Hold the ID more firmly, or less. Try different ways of displaying the ID. Make sure you practise it, and that it works perfectly every time in practice, before trying to show others.
I think that, as you've had the ID six weeks, that's too long to return it to the place you bought it, so that leaves the other possible solutions.
The most obvious thing to do is to try option d, in case it is just a handling problem. If it isn't, you'll need to get a new ID, or get something to sort out the problem.