I am a PhD graduate from Germany. Later, I worked in Germany for a year. I have had a blue card since 2015, which can be used to work in any company in Germany until 2020. But I left Germany and went back to India in 2016. I know that it has expired as I stayed out of Germany for more than 12 months.
What are the conditions and requirements to reactivate my blue card in order to work again in Germany?