Your provisional driving licence lasts till your 70th birthday. So if you have applied for one when you were 16, then it means you still hold a provisional licence. Therefore you cannot apply for a new one because you already have one. What you can do is request for a replacement one from DVLA. All you need to do if fill out a D1 form (application for a new driver's licence) and send it to the DVLA with the correct fee (£20 at the time of writing).
When you get your replacement provisional driving licence, you can then go ahead with your bike test.
