I am not sure but so far I could remember the pvz format was coming originally from Product View which was related with Creo Parametric / earlier Pro/ENGINEER and there we had a restriction to use only names using the characters a-z and 1-9 without spaces and any others characters. Also, the maximum name length was 31 characters. May be some of these restrictions is still remaining in some converter functionality.
Another point is that if you were able to import the fbx file successfully to an studio project ... in this case you can take a pvz file from the project directory. Because the converter does not use the native format but always create a converted copy to pvz format.
Please check Documents\VuoriaStudio\<your project name>\src\phone\resources\Uploaded
folder for the pvz file.
