D5 Render is unable to open v.2021.1 build 21.0.339 64 bit . had to re save the file as version 2020. Glad I opted not to go Pro version.
your own fault, 
then you missed one of the best render programs. 
I don’t think the problem is the D5.
Hello, you can try our D5-SU plugin, this is more convenient, and you can sync D5 with SU2021 directly. We will support opening skp2021 files in the future.
SketchUp Rendering (d5render.com)