My Mate 8 fell off a few weeks ago, and then I was dead. When I connected it to the store, the Huawei logo went through for a second and then disappeared again.
From then on, it was always at the slightest shock and I had to hit it on a certain edge, that it went again. Thought therefore that a contact or so slipped.
2 days ago I'm fumbling again and now I can't get it anymore, so I can only see the Huawei logo when I plug in the phone. Is the whole thing now on the battery? Finally "wants" the phone but can only when it is plugged in and then yes, right out again…
Would be very nice if someone can help me repair tool I already have!
So for me that sounds very much like a loose connection. The battery is broken by a case should not actually happen, then rather the contacts.
If you prefer fixing it yourself, just open it, take a picture of how it should look right and see if there's a cable loose somewhere and work your way to the smaller stuff.
Witzbold, no one can see clairvoyance here. If you have no idea, bring the phone for repair.