47US reboot after WIFI pairing

[Antarctic74]

Hello friends,
I have a couple of Yi Home cameras (model 47US) with firmware 0.4.1. After a change of router, during the association with the new wifi, one camera became unusable: it started up regularly until the message "waiting for connection", it read the qrcode of the YI app regularly and after the association process it rebooted itself.
After several attempts, I would like to try to restart everything from the beginning, so I am trying to restore the original firmware: I downloaded the file "1.8. 7.0A_201702081101home" (from the original firmware hack v3 folder), copied it to a formatted SD card, inserted the SD card into the camera and rebooted, but nothing happens, it seems that the camera ignores the firmware file. What am I doing wrong?
Is it possible that the camera cannot access the SD card?

[Antarctic74]

Never mind, I changed the SD card and tried to reinstall the V5 4.0.1 files and now the camera was able to connect to the wifi.