If you mean the rubber belt with teeth on it, first check it's still attached at both ends. If it can't move your head along its slider, it will be because the head is in the locked position.
There will be a little plastic release bar in front of the print head which is locked on the right hand side of your printer. Gentle push the release bar and you should be able to pull the print head away from its locked position.
When you turn on the printer, the head will move and reset itself, hopefully without locking this time.
If it continues to lock then the whole assembly on the right hand side of your printer has lifted slightly.
With the printer turned off and the head slid to the left (see above) put your hand onto the locking/cleaning assembly and press down and it should pop back into its seat.
Turn on the printer and it should reset.
If its the gold/copper looking sensor marker strip behind the print head you are talking about, this is held in position by sprung hooks at each end and the strip is simply hooked over protruding hooks. Attach one end then stretch slightly (compressing the spring) to attach the other. The head uses this to position itself when printing and it is a precise and essential piece of equipment. So be careful with it.
I hope any of this helped.
Nigel
The INK Store
http://www.the-inkstore.co.uk