ea3500 won't allow firmware upgrade

I have been having so many problems with comcast's technicolor tc8305c that I finally had an online tech bridge mode it. Now I hooked up my old ea3500 and the speeds are half of published when it's on wifi vs wireless.

I downloaded firmware and tried to update it but it gets to 98 percent and then fails. It claims there is no device on the network. I also cannot install smart wifi for the same reason but I am using the Internet and logging in to the router so I need help.