I have two GFCI outlets in my kitchen one each side of the sink. Each outlet then has three outlets after it which when the GFCI trips interrupt their connection as well. I feel this is pretty normal but I did not wire it. No work has been done in this room in quite awhile like years. Just this past week my vacuum sealer started tripping the GFCI when it’s pluged into any outlet down stream. It trips when the heating element turns on. Then last night my instapot tripped it. The instapot has read off that outlet for the two years we have had it. In that same series of outlets we have our toaster oven plugged in and it has never tripped it. I am baffled at what the issue could be. Is it possible that the gfci has an issue and needs replaced or do I have some kind of bigger issue and how do I test to see what my issue is.
If your vacuum sealer is like mine a plastic case with a 2 prong cord there is not a way for a ground fault , I would say that since you have 2 devices causing tripping and this has worked in the past. the GFCI is failing. I started using weather resistant GFCI outlets in bathrooms quite a few years ago because bathrooms can have very high humidity levels and the outlets being in walls can sometimes condense moisture similar to being outside. I don't normally use WR GFCI'S in kitchens because they are normally larger rooms and not exposed to such high levels of moisture. I would swap out the GFCI. The new ones have more sensitive electronics and constantly self test where older ones I have found failed (test won't trip on outlet or plug in tester) or trip for no good reason like a double insulated device with a 2 prong cord, so this should solve your problem.
A GFCI trips because of a third path
As you know, electric current travels in loops. That's why the two pins on your plugs, it provides the two paths intended for use.
Sometimes current leaks. If it does, it can follow a third path accidentally, and that is always some kind of bad. Worst being when the third path is through a human or pet.
One big reason for grounding is to be a sacrificial "third path". Better the ground wire get zapped than you! Another approach is the GFCI: since current flows in loops, the current on the two intended paths should be equal. If not, a third path has come into play. GFCIs compares flow on the two paths, and trips if unequal.
So..... For ordinary troubleshooting of a GFCI trip, look for that third path. Is the appliance sitting in a puddle of water (because your sink does that)? Third path. Does it trip when you touch the appliance? Third path. Does the appliance have a 3-prong plug? Third path.
Test the appliance
So our first diagnostic method is to forcibly remove that third path. Mop up the water, stop touching it, set it on a dry plastic cutting board, and if it has a 3-prong plug, get a cheater plug to defeat the ground. (Doing so will make the appliance dangerous. This is strictly as a test). If that clears the ground fault, the appliance is defective. Clean it thoroughly, let it dry out, and if that doesn't clear the fault, off to the repair shop it goes.
Other than testing, never run an appliance on a cheater cord with ground defeated. And if you must, make sure it is a GFCI protected outlet. (I.e. GFCI upstream of it).
Another test is to plug it into a different GFCI in kitchen or bathroom. If it still trips another GFCI, it's the appliance.
A Neutral-Ground fault
If one GFCI trips every appliance, either it is defective or there is a ground fault in the fixed wiring of the building. One classic wiring problem is a neutral-ground fault, because this fault alone will not flow any current. But when a load is placed on the circuit, the fault will flow some return current and cause a trip.
This neutral-ground fault could also be in any 3-prong appliance which is still plugged into the circuit. Some people go crazy trying to troubleshoot a GFCI problem and it never occurs to them to unplug a certain appliance "because that's always plugged in". This often proves to be the culprit.
If the GFCI trips some appliances and they test successfully on other GFCIs, then most likely this is the above-mentioned neutral problem, except the leakage is small enough that it only trips on high power appliances, such as those that make heat.