Can I submit a paper to a conference if I have presented it at another conference earlier but it wasn't published in proceedings? Can I submit a paper to a conference if I have presented it at another conference earlier but it wasn't published in proceedings?
Last year I submitted my work to a conference and it was accepted as a long paper, so I thought it was going to be published in the proceedings, but it seems they have a loophole in their rules. Long story short they they didn't publish the long paper. They published my other abstracts, but not the long papers due to this awkward loophole. I was planning to submit to a journal, but with the reviews and revisions, it will be a lot different from what I have right now. Can/should I submit the paper to another conference instead? One that will actually publish?
I am aware that in some fields conferences are the main repositories for new contributions. I don't know how it works and I do not want to enter into this aspect.
In other fields* conferences are rather venues to disseminate and discuss results and ideas, and, at the best level, doing it in a more interactive fashion than the one permitted by papers.
Moreover &quot;political&quot; motivations play a big role. Note the quotes... It can simply mean an authors is curious of meeting others, or seeking collaborations.
This means that

the same talk maintains its practical novelty for an indefinite time. It is up to the authors and to the organising committee to decide what is worth a presentation;

one can desire to enter in, or present to, a slightly different community.


As such, if your research is in *the other fields and you think you should submit you can surely do it.
Often one encounter the opposite problem. Namely the author already has a paper (paper or proceeding) and is barely interested in attending /presenting, while the committee asks for a paper to be published. This is a problem easily circumvented (everyone knows that it is not the case of self plagiarism) but it seems even not existing due to the loophole (?) you mention.
Summary: hard to say if you should. Most likely you can.