You need to do the following if you haven't already.
- Format Flash Drive to FAT32
- Create Folder on root of flash drive and rename to " PS3 "
- Create a Folder inside the " PS3 " and rename it " UPDATE "
- Rename your Firmware file (whatever it may be) to " PS3UPDAT.PUP " <---- Notice no " E " on UPDAT
- Now place the renamed firmware file (PS3UPDAT.PUP) inside the " UPDATE " folder
So it'll be like this on flash drive (PS3 > UPDATE > PS3UPDAT.PUP)
Note: All folders are case sensitive so make sure you are renaming folders and file properly
Now all that's left is to insert Flash Drive into your PS3 and go to System Update.
Hope this Helped