Onyx n96 - very disappointed

Last Spring I bought n96 from Onyx in China directly. I paid it with good workin money.
It is one of the most expensive ereaders.
Since last August 19 it does not work. It means it worked for few months only.
It is still under warranty.

I wrote to Onyx in China directly.
They quickly asked me a video. I sent it.
They sent me the update file
https://mega.nz/#F!AmAjBCDZ!8r2HHAqtyQ_EdU5ekuBA-g*
without any information on installation.
I asked them details on installation.
They sent me a file "N96 programming guidence", but it did not work.

From Onyx website a colleague downloaded updated.zip file of last May 9, he copied it in a micro sd card and installed it in my n96. The installation was successfull, but my n96 still not working.
Then he copied the update file ( https://mega.nz/#F!AmAjBCDZ!8r2HHAqtyQ_EdU5ekuBA-g ) they had sent me from China in my n96 and he tried to install it in my my n96. Bu my n96 said: "signature verification failed - Installation aborted". It looked me a funny story: I received in from Onyx and signature is wrong.
I wrote to Onyx in China again, in one hour they sent me a new file, I try to install it, but it is again "signature verification failed - Installation aborted"!!!! Funny stories? Or sad?

Can anybody gives mi advices? Thanks, I urge to use n96.