You may not be ready or not open to them enough. How strict is your idea of a dragon? If it's a setvideal, you may even be repulsing them. You may also need to open your third eye if you haven't already, as opening it can make spiritual connections very easy.
Hmm, try picturing the letters if possible in a calm state, one by one. If you don't lose concentration then you should be able to communicate with it in a sense, as directly speaking to spirits in deep relaxation is hard.
There are any ways, Dragon magick is all Astral craft, Dragons are part of only the Astral plane, Google some information on it, You may find help, Else if anyone claims to be having or seeing dragons ( On Material plane) are fake, as I've got from my practice outcomes.