First, I wasn't question-banned. Next, I asked a question. The "Ask Question" page had no warning on it. My question had a score of 7 (9 upvotes and 2 downvotes). Last, I tried to ask another question. It said, "Sorry, we are no longer accepting questions from this account."
Wait a sec! I asked a question with a positive score and it caused me to get banned without a warning? Why did this happen?
The precise criteria for question bans (which are automated) don't seem to be noted anywhere. In general terms, if you post "too many" "low-quality" questions, you will be question-banned. Neither of those terms seem to be rigorously defined in this context.
One thing that may be a contributing factor (I don't know for sure; just speculating) is that your post received a couple of downvotes in addition to the upvotes. Another possibility is the post's similarity to a previous post. I can only speculate, but if you work to improve all of your existing posts, as mentioned in the linked articles above, you can probably have the ban lifted.
Caveat: I am not an expert on this subject, and am only writing based on what I have gleaned from the above articles. If what I say contradicts what is noted elsewhere on Stack Exchange, I am probably wrong.
You were probably very close to a question-ban when you asked. Your profile shows a lot of questions from last year with negative scores, and there may be more that you deleted that aren't shown. I don't know if 8 or 10 upvotes outweigh 2 or 3 downvotes on a question, though I would expect them to. But perhaps not.
It's also possible that when you asked the latest question, one or more people looked at your old questions -- this latest one looks like it was pasted in from elsewhere and a person might wonder if you did that a lot, or if you tended to take the time to make up questions with nice diagrams. If that resulted in some more downvotes for your older bad questions, whatever the calculation is for the ban might now be "nope, too much bad stuff" not just from the new question, but from the old ones too.
Either way, fix (don't delete) the old things. If there are comments saying what the issue is, address them. Your edits will bump the questions, upvotes may ensue (the giant list of "posts that need upvotes" in your profile is really not the way to do it) and your ban may lift. None of us know for sure. I'm just speculating based on experience.
