Question about 16+ oyster

So I'm 18 and according to TFL if you're in full time education, you can apply for a 16+ (it would be a new oystercard but would be valid for only a year) but need a verification letter to school. I got the letter verified (university stamp, teacher signature etc), took my passport and a council tax letter as proof of address to the post office then paid the £20 admission fee. I assumed the I'd would be verified on my photocard straight away but it didn't? It still says awaiting ID verification? I called up TFL and they said you have to wait a week? I assumed the post office would verify it straight away. So IDK what to do.. Did something go wrong here or does TFL has to verify it themselves?