I would guess that it is a WIBU driver version thing. See:
http://www.graphisoft.com/support/archicad/downloads/WIBU.html
perhaps you need to reinstall 5.20b
(For OS 10.6, the converters work with the 5.3 and the wkmac.lib listed there.)
Cheers,
Karl
One of the forum moderators • AC 26 USA and earlier • macOS Ventura 13.2.1, iMac Pro 10-Core, Radeon Pro Vega 64