First let’s check the entire power cord and plug to see if it is damaged. If the cord is damaged, please stop using the unit and take the machine to an Authorized Service Center to have the machine inspected by a Quality Technician. You can find your closest one with the following link: http://www.bissell.com/support/product-support/service-centers
Next check to make sure the power cord for the floor brush is plugged in; if it’s not firmly plug it in.
Lastly check to make sure the filter is clean. If it’s not, clean the filter and place it back in the unit.