No this isn't about diff kinds of canabis sorry!

I have a bloc-paved patio in my rear garden. When it first got laid, no weeds appeared in the cracks for nearly 2 years. Now though, weeds grow at an alarming rate. No sooner have i pulled them out, they gow back a few days later.

What can i do? Weed killer doesn't seem to work! AM i using the wrong kind?

HELP!!!