Hey Qatar. ..I have the same issue. No Signal.
I have tried everything from
1- switiching inspire and rc off and back on
2- changing usb cables
3- changing tablet
4- trying other cables with other tablet
5- making sure antennas are points in the right direction
6- removing sd card
7- formatting and reinserting sd card
8- inserting new sd card
9- deleting and reinstalling dji go app
10- relinking rc with inspire
11- unhooking X3 from inspire and reattaching
12- talked to support and tried their steps
In the end they asked me to send them a hidden log file in the sd card, then replied by saying the file shows my X3 is faulty and i need to send it in for repair under warranty.
Funny thing is, although i get no signal, i have full control of the gimball and although there is no live feed i am still able to take photos and videos ( blindly ) but none the less the X3 is functional. I can not view the images or videos on the app, they wont come up, but i can download them to my camera roll on my ipad and they are there.
I have tried to comb the internet for any tips regarding this issue, but nothing. Clearly the issue is with the signal between camera and app. And i cant find out why.
Just to make thingns a little clearer, i have had no signal/no live feed from day 1. I turned my inspire on, rc on, launched app, then got the update requires list ( from aircraft, rc, battery to camera all need update). Turned everything off, googled steps for updating, followed the steps to the letter. Used videos on youtube as guidance, took a while, then when i launched the app, showed no more update required. But no live feed since then. Flying gets boring without a purpose. #help
Since you've talked with dji and they said you have a bad camera I would take their word for it and send it in for repair or replacement. .