No water flow is coming out of the sprinkler's head.
First, with the water turned on take out the adjustable cap and make sure that water runs clear from the barb. Secondly, check and clean if needed the adjustable cap of calcium and lime deposits or debris. Finally, reconnect the cap, turn on the water supply, and screw/unscrew the cap to the desired water output.
Leaking around the emitter’s cap.
This usually happens if the emitter cap is not screwed on enough. To fix it, screw the cap a little more. If this does not work, remove and screw the cap again, correctly, to fix the problem.
The 1/4" tubing is being blown off the couplings or the emitters.
This could be caused by the tubing not being fully pushed over the barb or excessive pressure. Reconnect the tube, making sure it covers well the entire barb, and check the pressure. The system should not have an operating pressure higher than 40 PSI. Additionally, you can try cutting the small section of the tube where the barb was initially connected and reconnect.
How can I help protect emitter heads from being damaged by small animals?
Squirrels and other rodents chew on the emitter trying to get access to the water. Providing them with other sources of water, easily accessible, can deter them from chewing up your emitters. Try filling small containers with water and scatter them around your area. If this solution does not help, you can use wire screen mesh to restrict their access to the emitters.