wontfix label is used when the maintainer has decided not to work on an issue.
Maintainers won't add this label lightly. Especially given there is an implicit recognition that there is something to be fixed.
The most common reason is that there is a completely satisfactory workaround — especially if that reason is documented. This label may also be used if the maintainer considers the issue to not be a problem in practice. Perhaps the likelihood of the issue occurring is just too remote, or requires exotic conditions to replicate. It could also be that the maintainer is simply unable to fix the issue because it is out of their hands, and the root cause is in software they don't control.
What can developers do?
It's possible that the maintainer hasn't fully appreciated the issue in question. Perhaps it seems a remote theoretical possibility to them, but is more likely than they appreciate. If you think this is the case, you can add more supporting information to the issue.