A little more information would be helpful. Does the vacuum seem to laboring indicated by a louder than usual noise? If you place your hand over the tube port with the vacuum on, is there much suction and does it change in sound as you plug the port and unplug the port with your hand? If it doesn't change or very little change is noticed, then the vacuum is plugged between the port and the vacuum itself. You can disassemble the machine and clean the port to vacuum line. Another possibility is that the vent in the case is plugged and therefor the vacuum doesn't have adequate air flow which reduces the level of suction. One last item to check is all the connections to see if any cracks or hoses have come loose. My last guess would be the vacuum is failing and needs to be replaced.
good luck
good luck