Allâh has set a seal on their hearts and on their hearings, (i.e. they are closed from accepting Allâh's Guidance), and on their eyes there is a covering. Theirs will be a great torment. (2:7)

Allah tells us in the verse (2:7) not to be disappointed when we are working towards his cause, conveying the message of Islam to non-believers, or non-practicing Muslims. And if one is not achieving the results then, he/she should remember this verse. They should realize that their hearing is closed, and they cannot hear good things which will benefit them here and in the hereafter. They cannot see good things because, there eyes has a curtain over it. 

Because of their sins and stubbornness,  Allah has already chosen them to be punished, while they are under the impression that they are smart and modern.  They do not have time to hear these type of things because, they do not know it's wisdom, and because of there own actions, there eyes and hearing has been sealed by Allah.

Note: However the doors of repentance are never closed until death, and we should cry and beg to Allah in order to open our eyes and hearing so we can understand the orders of our creator, sustainer, and our provider, we should always remember that Allah's mercy is more stronger then his punishments, if one tries to seek it within his lifetime, inshallah.