The toilet itself is plugged or the pipe from the toilet to the drain is plugged. It may be that the tub and sink have their own drain pipe that may connect to the main away from the toilet drain. Plunge the toilet or sometimes if you fill a 5 gallon bucket with water and pour it into the toilet as fast as it will take it, that will flush out the line. It is a greater amount of water all at once an forces out what the clog is.
Age isn't reason for toilet not flushing. Several things could be wrong for toilet not flushing.
As water drains, it displaces air in the pipes. If the vent or vents in your house are clogged up, the air must find another way out, which could be another drain in your house.
look in the tank and see if the flapper is working when turning the handle or then use a plunger or buy a toilet snake they are cheap. If you have kids or etc then maybe something jammed in the trap and if you can't get it out then take out the toilet and snake it backwards. If your toilet don't flush but the drains of other fixtures work fine then its something wrong with your toilet most cases. More information is actually needed to give a proper answer
Wrong adjustment
Sounds like the washing machine discharge is fitted to the main drain in the wrong place and it's discharge is filling your toilet. It's possible there may be something of a blockage just after the toilet, causing a backup. I would try to snake the the pipe from toilet out. You may even have to remove the toilet from the floor and do it there if there is no access underneath (like a basement or a crawlspace). I have snaked main drains from the toilets many times, and it's a pain having to re-re the toilet, but often it's the only way.
The main drain is plugged. You may need to remove the toilet and snake directly down the drain.
There may be something that is partially blocking the drain.
When a basin drains and causes gurgling sounds in other basins -- or the toilet, in this case -- it is usually a sign that a vent pipe is clogged or obstructed. The air being displaced in the drain pipe of the bathtub has nowhere to go if the vent is clogged and is being forced up through other drain pipes.
Age isn't reason for toilet not flushing. Several things could be wrong for toilet not flushing.
As water drains, it displaces air in the pipes. If the vent or vents in your house are clogged up, the air must find another way out, which could be another drain in your house.
Probably, yes because my toilet is making that sound ALL the time when you flush it.
Linkage going to flapper is sticking or needs adjusted. Nut holding flush handle to tank may need tightened or replaced. Pressure assisted toilet needs more force on handle to flush.
It could be a few things. There might be something partially clogging the drain(i.e. toothbrush, a cap to a hair spray can, pop-stick...). if this is not the case then you might have a calcium problem with the p-trap or syphon-jet. If your syphon-jet is clogged up, try to break some of the calcium out of the way so you can feel water flow through it when it is flushed. The syphon-jet it typically located at the bottom of the bowl. It basically makes the toilet flush. Without the jet your toilet should not flush unless it is located "in" the p-trap.
look in the tank and see if the flapper is working when turning the handle or then use a plunger or buy a toilet snake they are cheap. If you have kids or etc then maybe something jammed in the trap and if you can't get it out then take out the toilet and snake it backwards. If your toilet don't flush but the drains of other fixtures work fine then its something wrong with your toilet most cases. More information is actually needed to give a proper answer
If it's leaking between the toilet and the floor, you put the wax ring in wrong. If it's leaking between the toilet and the tank, you need to replace the gasket.
Either the toilet is plugged or the sewer line under the toilet is plugged. At this point I would suggest calling in an expert (plumber) to determine the problem. You have not given enough information to say. Sounds like you do not have enough water pressure coming in to wash the waste away. Check out the holes under the lip of the toilet seat to see if they are blocked, causing you to get an inefficient flush. Our new toilet is much better at flushing with lesser amounts of water.
The best way to check your sewer pipe is to have someone run a camera through it to see what is wrong. To prevent an accident, don't plant trees near sewer lines, don't park over a line, don't flush anything but waste down a toilet, and don't pour any grease down the drain.