A spool vanished at 0.2 mm
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If a filament you definitely own has vanished from a conversion, this is almost always why. Filafy hides filaments that cannot safely print through your nozzle.
Most of them are abrasive or particle filled. They are carbon fiber, glass fiber, ceramic and conductive filaments, and the metal, wood, marble, sparkle, galaxy and glow filled ones. Those can clog or wear out a small nozzle, and some do not bond well at a small line width. A few are set aside for a different reason, because the maker’s own guidance rules them out at that size. TPU, PC (polycarbonate), translucent PETG and translucent PLA are all listed as unsuitable for the smallest nozzle.
The Design step lists what it set aside under Excluded filaments, and why, so this is never silent. It is per nozzle, so the same spool that disappears at 0.2 mm is available at 0.6 mm.
You can turn it off under Settings → Printer, after acknowledging what it means. With safety off those filaments stay available, and Convert flags the risky ones instead of removing them. It is then on you to pick filaments your printer can actually print.