Why is the extruder only extruder only printing dots?

When the printer prints small dots like you described instead of one continuous line it is most of the time caused by under extrusion, this means that the printer isn't feeding enough filament to the hot-end/nozzle which results in the printer not extruding the amount of plastic needed to make a full line.

Here I will mention a few smaller things that you should look at before trying the other solutions.

Start with checking your slicer settings, maybe you have the settings for another material that has a lower printing temperature? Was the material that you used last time a plastic with a higher temperature, if so you may need to extrude some extra filament at a higher temperature before the new filament reaches the nozzle.

One common thing is small filament particles building up over time in the gears pushing the filament forward, thus ultimately causing the teeth of the gears to be filled up and they lose the ability to grip the filament.

If this is the problem you can solve it by cleaning the gears from the plastic particles, to prevent this from happening in the future it's a good idea to clean these from time to time.

The problem may be caused by the nozzle being clogged resulting in less filament than normally can pass through the nozzle, to solve this you need to clean the nozzle. I won't go into detail on how exactly to do this since there are a lot of good explanations if you search for something like "clogged nozzle 3D printer" and this answer is starting to get really long.

The original extrusion assembly is made out of plastic and therefore wears out after time, if you have marks or other signs of wear on this part or if the tension of the spring doesn't grip the filament that good you may consider buying a new one. There are metal ones available in most stores that sell Ender 3D printers.

It's common for elastic filaments to cause trouble with the extrusion due to them being elastic, this makes it harder for the extruder to move the filament at the speed it needs to be printed.

The stock Ender 3 printer has a so-called bolden extruder where the extrusion motor isn't placed directly on top of the printer head, elastic filaments are extremely hard to print, if not impossible with a system like that.

If the printer is modified to have a direct extruder (placed directly on top of the print head) it still may cause under extrusion, to solve this you can higher the flowrate percentage in the slicer settings to counteract the properties of the elastic filament.

Hope one of these solutions helped and good luck!