I had the same problem and this fixed my issue
Credit to _alexndr
Actually I upgraded to Lollipop and then when I ported Kitkat Rom in order to downgrade to 4.4.2, I got "baseband unknown" and everything gone ( IMEI, Mobile Network, Camera, Sound and ...).
What I did ( note my phone has been updated to Lollipop baseband and bootloader, and my below instruction might give you some hint if you are on some other Roms or bootloaders).
1- reboot to download mode (holding power,volume down and home buttons)
2- Applying these three files vie Mobile odin 3.09 PC.
>> BL_N9005XXUGBOB6.tar.md5 <<
>>AP_PERSIST_LP_N9005,tar.md5<< Attachment 3268020 ( you need to unzip the file ) / P_PERSIST_LP_N9005,tar.md5 is not necessary and you can leave it blank.
>> CP_N9005XXUGBOA1.tar.md5 <<
3- hit the start button on Mobile odin PC. and sit back to finish its job.
4- Go to mobile recovery mode in order to wipe/factory reset data ( holding power, volume UP and home buttons at the same time).
5- Reset the phone. It will take time to boot up and then good to go .
BTW my knox still is 0x0.
After trying to downgrade from Lollipop 5.1.1 from temasek back to 4.4.2 stock via the link from Samsung updates to the XSA Australia version, or the international UK all version, waiting to download the TGY now to try that now my phone wouldn't boot, it was giving the error down the bottom. After I reinstalled CWM Recovery, I can now get back into Recovery but when trying to install the OS again it says encryption unsuccessful an I need to factory reset my phone. I've tried that but it keeps coming up .
I have access via ADB and recovery, any idea how i can get this fixed?
Ideally I want to get it downgraded too...
I use CWM 126.96.36.199. Any tips what I should try? The OP posts links aren't working to try the 4 file ROM method and wondering if I need to Root via Odin or re-flash CWM first but hesitant to try until I get some advice from someone that knows these android devices better... Any tips appreciated?
Error message when flashing Stock is below
<OSM> Enter CS for MD5..
<OSM> Binary Check MD5.. Do not unplug the cable..
<OSM> Please wait..
<OSM> Checking MD5 finished Sucessfully..
<OSM> Leave CS..
<ID:0/004> Odin engine v(ID:3.1100)..
<ID:0/004> File analysis..
<ID:0/004> Get PIT for mapping..
<ID:0/004> Firmware update start..
<ID:0/004> NAND Write Start!!
<ID:0/004> FAIL! (Ext4)
<ID:0/004> Complete(Write) operation failed.
<OSM> All threads completed. (succeed 0 / failed 1)
thanks in advance!