Dear Teodor,
Yes, the bin is a mesh sequence not particles (btw its realflow5 but maybe the mesh format is the same?). What i sent is a the first frame of 700, however the mesh only first appears from frame 101, and that is why the tool failed. When i moved frame 1-100 to a sub category temporarily while generating the proxies it works to generate finally! Great. Maybe allow empty realflow .bin files for processing to vrmesh from now? since this is not easy to understand if you wouldnt have told me i would have thought the entire sequence is incompatible 
Again, thank you very much for your kind help.
Best regards,