Skipping of material

I generated a document and it had everything (30 cards) from my pdf a week ago, today I generated the same document and it gave me only 11 cards .. is it because I have the free plan? I am facing the issue also with other pdfs that I generated.. I could go through my lecture and the ankis would fit perfectly with the material but since couple of days it seems as its not generating questions for everything in the pdf but it’s more skipping parts..