Here you have the translation:
HOW TO RESOLVE THE SIM CARD READING PROBLEM ON THE LETV X800
1-download the firmware from HERE
2-don't rename the file, enter into the TWRP recovery> advanced wipe> wipe cache / dalvik cache / system / data (except internal storage, be careful!)
3-install the firmware that you have downloaded as in step 1
4-at the end of flashing, clear again Dalvik Cache and reboot the system
5-enter into settings menu, open the Restore Factory Settings menu and click on Reset Phone (remember to include format virtual SD card), the phone will restart and clears the TWRP recovery restoring the original stock recovery;
6-now, download the firmware from HERE
7-rename the downloaded file into "update.zip" and copy it to the root directory of the Letv phone;
8-turn off the phone, then turn it on pressing the volume up key + power button until you see the LeTV's logo on the screen, release immediately the buttons and enter into the stock recovery;
9-click upon "Update system with zip";
10-very important thing: you must confirm "clear data";
11-power off the phone and turn it on again.
IMPORTANT: if the stock recovery will appear in Chinese instead of English, you have to consider that the buttons position is the same as the one reported in the figure above (depending on the version), so you can easily select the proper button as in the attached figure!
When you restart the phone (be patient, the boot will be very long) the sim cards will be read normally.