Hi Kandi
There are several possible problems with these tricky low notes.
Fingers – make sure all your fingers really are fully covering the holes.
Breath and tonguing – both need to be gentle, so imagine making a daaah sound, rather than tooo. Sometimes you need to just breathe without tonguing at all.
Instrument – clean and dry (warm it up before playing, check inside for lost cleaning stick!). Make sure all the joints are fully pushed together.
Sarah Jeffrey on Youtube has a good video on how to hit the low notes.
