Everything related to the integration for SketchUp.
Apologies, but it has generally been the case that an earlier version of Maxwell cannot read files written by a later version; if 3.x was able to read files written by 4.0, I would consider that to have been only a temporary condition, and not indicative of any official support for such (feel free to ask tech support if you like, via https://portal.nextlimit.com). The official convention, if I am not mistaken, is that any version x.N should be expected to be unable to read files written by a subsequent x.(>N), so it should be the case that what you report applies not only to 3.x, but to 4.0.x as well.
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