saving DXF files in unreadable format

i recently update to DS standard 2025 spo x64. i use it mainly to prepare dxf flat drawings for use with a plasma cutting machine.

it has worked fine since installation mid january.  

i was off for 3 days last week and when i returned, the drawings i saved will open on the pc but when i send them to the plasma cutter on a usb drive , the plasma machine show a blank page.   as far as i know nobody else has used DS for any reason and the software on the plasma machine has not been altered updated etc.  is there a setting that i may have inadvertently altered without realising it?

how can i restore the original installation settings ? i have reinstalled the DS software and this has had no effect.