Why aren't I able to revert back to Windows 8.1?

[Windows Central Question]

Not able to revert back to windows 8.1

Hi,

I am trying to revert back my Lumia to windows 8.1 by installing Windows phone recovery tool. but I am getting error message at the end of download as

invalid Cr32 for file : RM821_3051.50009.1424.0009_Retail_im_india_443_09_441109_prd_signed.ffu

Please suggest.