nanoCAD 5 cannot open a dwg2018 file

please check the version of .dwg file, because nanoCAD 5 cannot work with dwg2018 format.

How to check dwg version: open the drawing file with any text editor (notepad, for example). At the beginning of text you will see the following code: AC10XX, where XX can be: 32, 27, 24, 21,...

AC1032 code means that the file has dwg2018 format. You can use Platform nanoCAD to work with these files https://nanocad.com/products/nanocad-platform/.