zp ******s not working?

Hi, I have successfully completed a lot of ******s. But it seems as though you only get zp from doing ******s once every 2 weeks.
If I do a ****** after not doing a ****** for 2 weeks, i will most likely get my zp, but if I do ******s two days in a row, then it won't work.
What's wrong?

It's obvious, half of ******s doesn't work.

I think sur.veys are all luck, like crates ._.

try the cheapest and free ones.
i always do the 1000-2000'ish ones
and they work
or else go for the 100+900 zp ones it may be few.
but man they work. and they give a bit more BP than usual