Xsara Picasso Motor Change does not start solved

Hello everyone, I tell you for the despair that I already have, it turns out that it is the second time that the engine was changed to my 2004 Picasso, in the first change no problem was changing the engine starting and leaving throwing but after 2 months it was broken again (it is what you have to buy it to an individual) and now it turns out that I bought another scratch engine with warranty and proven but what is my surprise and the mechanic that the engine is not Start in Economic mode and leaves in the immobilizer box, and tested with the key with control and with the replacement that came from manufacturing nothing at all the car does not start, and looked at all the fuses and they are fine, and removed the battery for 30min and neither, and looked if Gasoil arrives and if it arrives. My impression is that something is cutting electricity since it does the same as when it takes shit in the key and you have to find the nail to take it out in the immobilizer box, I am told that the heaters can be but looking in forums indicate that the HDI only use the heating when there are temperatures below zero so I have no idea what can be happening. Please ask you if you can give your opinion of what may be happening. Thank you all in advance.

Hello, how did you say the problem is in the immobile you should not recognize the key

Hello, thanks for your answer, it turns out that yesterday I went to the workshop to see if 2 thinking heads found the problem and if we found it, I had the fucking tree tree sensor and a 20A fuse that is in the fuse holder in the capo, after changing that I started the first and removed the economic mode and the immobilizer with what is already solved.