Very strange: Google keeps on sending 2-step sms

I have 2 phones: an android one, sim-less, that I use only on wifi, and an old Nokia I use everyday (charging it once a week, which is what I need) I enabled google 2-step authentication on the android one, and for some reason I could not use the code I had received. I received another one afterwards which I used successfully. Now every hour or so I receive an sms with the first code, and it has been so for the last 30 hours... Any idea of what is going on? Thanks