Update Failed and locked Prime

[parisse]

You can perhaps try with the current firmware files
https://tiplanet.org/forum/archives_voir.php?id=658248
and usbtool
https://tiplanet.org/forum/archives_voir.php?id=19616
Erase BESTAARM.ROM, MASTER.DAT, APPSDISK.DAT.
Update the file usbtool.ini with the current firmware filenames, i.e. in
UpdateItem01 = .\BESTAARM.ROM 0 0x00000000
UpdateItem02 = .\MASTER.DAT 0 0x00100000
UpdateItem03 = .\APPSDISK.DAT 0 0x00500000
replace BESTAARM.ROM with PRIME_OS.ROM, MASTER.DAT with PRIME_MASTER.DAT and APPSDISK.DAT with PRIME_APP.DAT
Reset the calc with SYMB key pressed, run usbtool on the computer, then Update and select the 1st file, then 2nd file then third file. Reset the calc.