Thanks for your reply, I also contacted ProMotion Nest Software Engineers and thought I would share this with you all for future reference.

"AutoCAD LT should be all that you need. R12 DXF is the preferred format.

The problem with splines and ellipses is that in CNC world we have only
two kind of elements: lines and circular arcs. Splines and ellipses are
neither, so they need to be converted to lines first. Some CAD softwares
can do this and I suppose AutoCAD LT can do it also.

Please note that CADs use to have really high precision and thus they
make the conversion to lines so that a curve is converted to hundreds
of really short lines. I don't know, if there is a setting for the
precision of conversion, but if there is, it's a good idea to set it
around 0.01". If the final cutting program includes hundreds of small
arcs, it takes longer to load it to a CNC controller and it's more
likely to cause other problems as well.

Splines are not supported in ProMotion Nest, but v4.22.1 (current
version) supports ellipses and partial ellipses. Ellipses are
converted to lines by Promotion Nest."

So now I am waiting to be directed to the updated version of ProMotion Nest, hopefully it might solve some problems.

Thanks again for your help.
Michelle