I've faced this issue before and I tried know 4 different methods. There are several reasons that can cause this error. I cant explain every step in detail but I think anyone who is facing this issue would be able to understand or you can read this article: [https://clouttechie.com/no-bootable-device/|Fix No Bootable Device Error] (Thoroughly explained)
One of the following step will sort out the problem:
1. Are you using a tool to make your removable device bootable? If not, then create a bootable Windows 7 USB device via Rufus.
2. Restore the Operating System
3.Using following CMD Prompt:
bootrec /fixmbr
bootrec /fixboot
bootrec /scans
bootrec /rebuildbcd
4.Re-Install or Reset Windows