Hi.
Even if you are using the EU firmware I would expect you to have a camera connection within about two minutes and (apart from the possibility of it dropping out when raising the landing gear as I mentioned in my post above) should keep that connection while within reasonable VLOS.
That leads me to ask a couple of questions:
What video antenna are you using? The patch or the mushroom?
If the patch, are you pointing the flat part directly at the aircraft (the patch is highly directional)
If the mushroom, are you pointing it straight up? It works better if pointing straight up.
Have you checked the antenna on the aircraft?
If all flying controls work then you haven't lost RC signal but just for the heck of it, what direction are you pointing the RC antenna? This needs to be pointing straight up too.
As I mentioned in my previous post, a TH using EU firmware is prone to loose the video connection at the time that you raise the landing gear. Not every EU aircraft has this quirk but a good proportion does. However, it has been noted that once the camera has re-connected, it seldom looses the signal again for the remainder of that flight. One way to force this second (supposedly) stronger connection before you even take off is to wait until the initial camera connection has taken place then force a re-bind to the camera. Doesn't solve the issue but does tend to make the loss of video on raising the landing gear slightly less of an issue.