Ah ... that the reason.
Solidworks 2019 files will load 2018 files but not the other way.
You could download the STL/STP/IGS version of Orion and then open the STEP files. Solidworks 2018 should hopefully convert them over.
You can then save them as solidworks 2018 SLDPRT / SLDASM files.
hope it works :-) Mark