[AC Question]

Hi ,
Today ,and after i've downgraded my phone(Xperia z1 c 6903) back to kitkat 4.4.4 , i noticed that my phone cannot detect my sim card and i also noticed that my baseband is unknown .
Help please

[Rukbat]

Try a simulated battery pull (hold the power button down until the phone restarts), then do a factory reset (make sure you back everything up first - Backing up an Android Device - the reset will delete it all.)

If that doesn't do it, download the 4.4.4 ROM again (preferably from a site posting the MD5 or SHA1 and run a hash program on the download to make sure its MD5 or SHA1 is the same as the one on the site), then flash it again. The baseband is the modem (the firmware that runs the radios). A bad baseband flash could affect the phone's ability to detect the SIM card.

[itguyjax8430]

Hi ,
Today ,and after i've downgraded my phone(Xperia z1 c 6903) back to kitkat 4.4.4 , i noticed that my phone cannot detect my sim card and i also noticed that my baseband is unknown .
Help please

You may want to make sure that you downgrade the baseband as well. Some ROM's may not include the baseband file. You may be still on the updated baseband.