Hello everyone encountering the same problem!
I found a solution to this issue. Not necessarily the same for all but in my case,i hadn’t installed the twitter app on my cell phone prior to filling the application form.
So i would suggest people to first install the twitter app on your mobile phone, log in to the app like usual, and then fill up the application form. Having followed this procedure, i have successfully obtained my api,secret key!
Hope it works for you as well!