IMEI null, can't make any calls topic

So, when I type *#06#, the only thing that I get is IMEI null and I can't make any calls. Tried many times to switch the operating system from 4.2/4.3 to 5.0 but doesn't work, please, don't ask questions about it, because the phone isn't mine, that means I don't have acces to it whenever I want, so please, any solutions ? :)

Null IMEI topic

Hello all.
Here's a summary of what I did before the imei was null and the baseband was unknown.
I had ressurection remix (android 5) and I tried to flash via CWM another rom (more exactly the albe95 Lollirom 0.99) and it crashed when flashing. It gave me an error and from there or It remained stuck on Galaxy s4 logo.
I did not panicked and I flashed a stock rom via odin. After I finished flashing the phone does not have any signal ,he baseband version sayts "unknown" and the imei is null/null.
I tried to flash a modem via odin but it gave me an error (something like the file "could not be opened (line 2012)" )
I don't know what to do next. Any suggestions?

Edit: I tried to download the S4 fix imei null and flash it via odin but it gives another error "md5 hash value is invalid"