The name of the temporary graphics file generated by the image region contains a mix of slashes and backslashes as path separators. At least this happens for svg images and inkscape can't cope with that. The file is generated but the system misunderstands the path name:
The proposal is to consistently use the system-dependent path separator character in the plug-in.
Inkscape seems to be a bit picky about such path names. KolourPaint, which I use for png editing can handle these file names.
SMath Studio: SMath Studio Desktop 0.99.7202.1420, 64-bit
OS: Unix 5.3.0.18; Ubuntu 19.10 - "Ubuntu 19.10", 64-bit
Screen: 1366x768 px, 96x96 dpi, 96 GP.CDPI
Localization: language=ENG; dec.symbol=<comma>; arg.separator=<semicolon>; OS dec.symbol=<comma>; OS arg.separator=<semicolon>; OS d.g.separator=<period>
Framework: MONO 5.18.0.240 (Debian 5.18.0.240+dfsg-3 Mon Jun 24 08:50:44 UTC 2019)
Plugins:
- [AppDir] Area Region - 0.99.7202.1420
- [AppDir] HTMLFileType - 1.14.7202.1420
- [AppDir] ImageFileType - 1.11.7202.1420
- [AppDir] Math Region - 0.99.7202.1420
- [AppDir] PictureRegion - 1.10.7202.1420
- [AppDir] PlotRegion - 1.11.7202.1420
- [AppDir] SMath Viewer Files Plugin - 1.1.7202.1462
- [AppDir] SMathFileType - 1.11.7202.1420
- [AppDir] SpecialFunctions - 1.12.7202.1420
- [AppDir] SpecialFunctions - 1.12.7202.1420
- [AppDir] StandardToolboxButtons - 1.1.7202.1420
- [AppDir] TextRegion - 1.11.7202.1420
- [AppDir] XMCDFileType - 1.12.7202.1420
- [UserDir] Development Tools - 1.0.6974.21980
- [UserDir] Image Region - 2.99.7100.21996