YAY!!! This finally fixed it ... from the developer in post on Aug 6, 2017 4:09:07 PM ... run in cmd line:

"C:\Program Files (x86)\Java\jre1.8.0_221\bin\javaws.exe" -J-d64 http://www.sweethome3d.com/SweetHome3D.jnlp

Thank you, thank you, thank you!!!!