I had to perform a reinstall of Ubuntu so I could do a clean install using APT derek@Derek-R540:~$ sudo apt install sweethome3d

WRONG!!
The instruction from download page DON'T suggest such actions.
To solve Your problem You MUST FORGET REPOSITORY VERSION!
So:
1. sudo apt purge sweethome3d (to clean repository installation);
2. Follow STRICTLY the instructions from Download page:
-download->extract->run the SweetHome3D.sh file.
Simple as this!
It work on every linux and with every SH3D version from 3.0 ~ now.
If You steel need help we are here to help you [>:D<]

You clearly ignore my first message and previous remarks in this forum.
You may have tested it on YOUR machine(s) the procedure DOES NOT result in a workable Sweethome 3D ON MY MACHINE.
As there are no error messages i cannot provide assistance as to why this is happening, starting Sweethome 3d result in a spinning pointer that stops no SH3Dscreen is opening.
SO unless you can provide me with terminal commands to execute that provide you diagnostics info I cannot further describe how SH3D fails to work
Further more all my previous work in SH3D will be lost

please check you comments

2. Follow STRICTLY the instructions from Download page: -download->extract->run the SweetHome3D.sh file.
Simple as this!

because there is no .SH file in the archive. the sweethoms3d file has no extension