Do you hear the pump running? Carefully check both the foam gasket on the base, just behind the heat element as well as the top foam gasket for attached debris. Most models also have a small plastic drip tray at the bottom (behind the heating element) that collects moisture as its dropped into the plastic tray slot inside the foam seal area. The top foam seal is cemented on, so dont attempt to remove it, but the bottom foam gasket is removable and can be cleaned underneath it as well. If the pump has ever been exposed to actual moisture, it could have been damaged. Any trace of moisture of any kind that can get pulled into the pump will cause it to fail. Mine also has the external vacuum port on top, but that also relies on the foam gasket to make its internal seal properly. If the vacuum port hole is 'stuck open' it can cause the vacuum loss, so try placing a finger firmly over that small vacuum port hole on top to see if its pulling a vacuum there when you start it to seal a bag. If it is pulling on your finger, the unit may have to be replaced. You can pull out the black foam seal on the bottom and wipe under it with a damp cloth or paper towel. Any trace of lint or debris in, and on the black foam area can cause a loss of vacuum. If there are any tears on that black foam gasket top or bottom, it will need repacement. I just removed the plastic tray on mine, that collects moisture, and found that the end that is to the right of the gasket, had some dried up stuff in there, which I wiped out. Finally, the plastic bag material should be quilted like the original FS rolls and bags. You can seal regular zipper plastic bags, but they will not be as effective in removing the air from inside.
Here, I use a seperate vacuum pump for my higher vacuum needs (pickled pepperoncini, meat marinades), and that unit has an 8 ounce capacity moisture trap that catches every single drop of liquid that might get inside the hose. Lucky for me, even if it did, the special vacuum pump has rubber diaphrams that can be cleaned easily.

Suggest that you call their customer service on Monday.

Here is a link that might be useful: FS replacement parts.