Otherwise all that air simply goes up the vent for back to back lavs there are only two ways to remover a blockage.
Back to back sinks clog.
Keep feeding more of the snake into the drain.
Remove the p trap with a screwdriver or wrench depending on the fastener type used on your model.
How can i solve this.
To use a drain snake remove the sink strainer and insert the tip of the augur down the pipe and twist the hand crank which releases the wire cable.
Snake from the lavatory roof vent and or.
This option is free so you can give this one a go first in order for you not to spend any money.
Baking soda and white vinegar.
Place the hose end at the entrance of the drain then create a tight seal around the end of the hose and the drain.
The pressure of the vacuum should dislodge the clog.
While you re waiting for the water to heat remove as much standing water from the sink as you can using a mug or small pot to bail out the water.
Attach the wet dry vac hose to the stopper pipe.
2 air guns only work when the clog s between the air gun and the vent.
Place a bucket beneath your p trap.
Then pour the entire kettle of water into the sink and wait.
Because the clog will be found below and downstream from the cross and.
This is the vertical pipe that goes up to your sink basin.
If the water stands in the sink and the clog doesn t move give the water time to cool and remove it to try again.
When you open the cabinet that is below your sink you will see some pipes.