lumia 640 - can?t install insider preview after a re-install

[Windows Central Question]

I`m a insider and my lumia 640 was working in insider mode. After a complete reinstall (downgrade to win 8 and upgrade to win 10 phone), I can?t active insider builds anymore.
I open download insider Preview builds and hit first steps. After a while, the lumia 640 tells me, that I`m not connected to internet, what is wrong !

How can this problem to be fixed?

 

[Mad Cabbie]

You are not alone. I rolled back because a couple of apps crashing. Don't know why I did it as I don't use the apps!! Now, like you, I can't get back in. " connect to internet" yet I am on Edge reading stuff about curing it. I don't like Bing either, got Google as the search engine. Before I could bounce a couple of emails around and it worked. This time no luck. I wonder if it's an issue their end??

1) I have HR and not restored back up
2) Swapped insider emails
3) Rebooted router, despite connection
4) Found a brick wall
5) stood in front of brick wall
6) Banged my head against it!!