Are you running Snap Orca on Windows or Mac? I’ve seen reports of various import issues on the Mac version.
Regardless, you should try the online converter (https://bl2u1.nbn.cat), or you can clone the GitHub repo to your machine if you prefer more control over the conversion process.
Online converter is great but it strips out setting like custom painted supports. Is there nay wya to retain all settings but just change printer model to U1?