It can be frustrating at first to have a question shuttled around like this, and it may be more so for a relatively new user to Stack Exchange. The cure for that feeling is to ask more questions, either related to Dyson Spheres or to new related or unrelated topics. That can at least dilute the feeling. Give Stack Exchange a chance, it's a wonderful resource and great place to interact with others in technical fields and to often get insightful answers and links to helpful sources, though for any specific question there's no guarantee.
Some of the workings of Stack Exchange may on the surface appear to make no sense or to be counterintuitive at first, but generally these behaviors are the result of years of experience and literally millions of question and answer posts, and have evolved to be the best overall solution for the majority of situations.
Migration and return
Comments there show that I was involved in helping to close the question in Astronomy SE (where engineering a Dyson Sphere around our own Sun will be 100% off topic), adding some modifications that might make migration more likely to succeed, and suggesting Space SE as a possible migration point, a bit like I did with this other space engineering question also originally posted in Astronomy SE.
What can I do about this problem?
I'm not exactly sure what "this problem" means; what happened is an understandable and by-the-book scenario. While question authors have a lot of "say" about what happens to questions, we are not the actual owners of questions in that we don't have 100% authority over what happens to them. Migration happens beyond our control.
I first learned about that when I wrote No Migration Without Representation! almost 5 years ago :-)
A possible strategy moving forward
- I think there's nothing you can really do about it being off-topic in Astronomy; there was never any chance of getting an answer there.
- There was a chance of getting an answer here in Space SE, but it didn't fly. As @called2voyage points out there's no guarantee a migration will stick, or that it will lead to answers.
- This may be the best outcome for you because it is now closed in Astronomy SE, which means if you now posted a different but related question in Space SE it would be a fresh question, and not a rehash of an existing closed question in Space SE.
How should your new question differ from the old one?
- It should show evidence of research. Sir Dyson may have already addressed some of your concerns, and later thinkers may have addressed more of them. Do a little reading on Dyson Spheres and their variants in Wikipedia and see if blotting out the Sun as seen from Earth has already been addressed.
- Check on what's already been asked and answered here in Space SE to make sure your concerns have not been addressed already, so that you can post a different question that won't be closed as a duplicate. Note that there are about 40 posts containing "Dyson" and a lot of these are about Dyson Swarms which have some benefits but don't blot out the Sun completely.
- Include links to the existing questions that relate to your question within your question and include a short note explaining that they are helpful background but leave unanswered the current question you are asking.
Just for example, you might ask something along the lines of:
Would a Dyson Swarm smaller than 1 AU frequently blot out the Sun on Earth? If so, how can we estimate how long the eclipse would last and if it would be a total eclipse or only a partial (umbral) eclipse?