Default S4 i9505 IMEI null + EFS Pro

Hi,

to begining, i'm sorry for my bad langage, i'm not english and it's difficult to speak on this tong to me.

I've Samsung Galaxy S4 i9505 on 4.3 with IMEI null/ null. I try to fix it with EFS Professional but i can't because i've an error.

- My phone is rooted
- I've Busybox pro and i use on v. 1.20.2 (only it work better)
- I use EFS Professional 2.0.80 (other don't run adb)
- 'ive S4 driver
- I've EFS Floder save with root explorer but it was save after imei null/null problème and few restoration.
- I've already try to flashe with my countrie firmware

I try to write my imei with EFS pro and i proccess like that :

1 - Run Busybox and wait all is load
2 - Run EFS professional
3 - autoriser l'accès avec l'option de débogage usb
4 - Wait result

That remains blocked in " checking device status..."

Have you an idea to my problème ?

2 - I've à second question, i have an galaxy S3, can i increase his imei, write the imei of my S4 and copy his esf folder on my S4 ?
3 - If i try to update on 4.4.2 to keep a chance to find my IMEI, can i Downgrade on 4.3 after ?

Thanks you for advance