MichaelBelgium looking at log records may be insufficient. Because too many topics and user forums, there is a transition problem and this problem is not recorded in the log file.
MyBB -> FluxBB -> Flarum
I successfully performed the transition scripts.
I'd appreciate it if you tested it. So I don't have to deal with FluxBB. Although all errors in log records are corrected, it still gives error. Even if I activate Debug mode, unfortunately there is no error. As a result, we don't know what the mistake was.