Hi there! I'm here to review your 250 Box Challenge and hopefully give you some tips on where you can improve. =)

Not extending your lines

First things first, there are a lot of boxes that are missing their extended lines to check the convergence. This step is mandatory! Checking the convergences is how we improve in this challenge. The objective of this challenge is to get all 3 sets of lines to converge to a single point (to their vanishing points) and if you don't extend your lines, you have no way to know if your box is correct or not and to see where you made a mistake.

Extending lines in the wrong direction

When you actually extended your lines, some of them were extended in the wrong direction. Remember that your converging lines should go in the same direction of your initial Y.

Direction of the extended lines - Look at the red arrows

I'll extend some of your boxes to check the convergence. =)

The lines that are a bit thicker are the initial Y. They tell me in which direction I should extend my lines.

Hatching and line weight

While optional, they help us tremendously to understand which sides are the front and inner sides of the box. Hatching is also a great way to improve the quality of your lines. I noticed that on the very few boxes that you actually hatched, your lines were usually wobbly and the lines arced a bit. All steps are equally important, so take your time when hatching. (Same for the line-weight).

Lines

While the quality of your lines improved since the beginning, there still is space for improvement. Your lines sometimes were wobbly or were arcing. There are some boxes where your lines are actually good (like on the page 59/250), they're confident and everything but then there are pages later on where your lines are worse than usual... :(

Conclusion

While you didn't follow the instructions carefully and ignored a few rules, completing the 250 Box Challenge, even if partially, is a big achievement.

Sadly, I can't mark your submission as complete. :/