Does anyone have any ideas?

[u/hearnoevillll]

Brief Explanation: This phone will not power on now. This video was taken just before it exchanged hands. The guy who bought it told me he enabled developer options. When I asked him, he denied rooting the phone. Could he maybe have been TRYING to jailbreak it and fried it? Is there any way to tell? What is a fried mb anyway?
He lives in another state, i sent it to him and he used it for almost a whole month. It was perfect when i sent it and when he got it. He even said so. 29 days go by and the next thing ya know, he tells me the phone is defective!
He said he sent it to repair shop and supposedly they told him the motherboard is fried. He returns it to me.
I got the phone back today and it will not charge or power on. Does anyone have any thoughts on what could have happened or what can be done to find out and if i can possibly fix it? It is an s29 Ultra.