I answered this question. I'll quote a passage:
This step requires medical technology that would also allow to transplant a human brain, because if a computer can be connected to the nervous system of a human body, then a human brain can be connected to the nervous system of a human body with the same procedure.
(emphasis mine) and later
I need a medical or technical solution to this logical contradiction.
There have been some claims that the question was actually asking something different, that we should assume that brain transplants are possible and can be done in any circumstance where the brain is intact enough to download. At best though, that is indeterminate. We have these passages that clearly indicate that the asker thought that a brain transplant was just as easy as the artificial implant. That the two require the same procedure.
At best, this is confusing. But confusing should not be read narrowly according to a reader's interpretation. I answered the question as per my interpretation. If my interpretation is incorrect, then the asker should fix the question.
When I read the question, I see it as "Because we can implant artificial brains, we must have the ability to transplant brains. But if we can transplant a brain, why didn't we just do that?" Many are taking "we must have the ability to transplant brains" as a premise. But I don't read it that way. I read it as a consequence of the premise that "we can implant artificial brains". But as I explain, it is not a required consequence. It is quite possible that an artificial brain implant be possible but a natural brain transplant not.
My answer pointed out that it is not necessarily true that a brain can be transplanted if an artificial brain can be implanted. It is strictly more difficult to transplant a brain than to implant one (my answer explains why this is so and doesn't need to be repeated here; I ignore the problems with creating an artificial brain and downloading to it). So there is no logical contradiction. Implanting an artificial brain is possible; transplanting via that same procedure is not.
This can be viewed either as a frame challenge to the premise that an implant being possible necessarily means that a transplant is possible or as additional information. Either view is possible, and either way, it answers the scenario in the question.
It shouldn't matter as rightness/wrongness is not a matter for deletion. But there seems to be some confusion about what I'm claiming. I'm not claiming that it is impossible to reattach blood vessels. I'm claiming that it is impossible to keep the brain alive while disconnecting and reattaching blood vessels.
A typical transplant cuts the blood vessels (and all other connections to the body) of the organ or body part. Then the organ or body part is put in a sterile container inside ice or other coolant. Then it is transported some distance with a delay that may be hours. Then it is attached to the new body, including blood vessels and nerves.
That process fundamentally won't work with a brain. A brain subjected to that treatment would be dead and destroyed. A brain that loses blood flow (and oxygen) dies in minutes, not hours.
As I put in my original answer, the process needed would likely have to keep blood flowing almost continually. This would likely require an artificial blood source that could be connected as the brain is removed from the original body and replaced as the brain is implanted in the new body. And it's possible that we might figure out the nerve problems prior to figuring that out.