Do you think that removing the ssd will help?
It's a sanity check to help you rule out things like unintentionally booting from the wrong device. Can't boot from hardware that's not there! If the USB does work with it removed, then something you believe about how the device boots is false and you can then try to figure out what. A lot of BIOSes will "helpfully" try the next device in the sequence if it can't successfully boot from the first one -- which can be really confusing when debugging.
Some other thoughts for things to check: does the device confirm that it can actually see the USB drive in some way? Does a USB keyboard work in the port you're using? If there's more than one USB port, have you tried a different port? Do your USB drives work in another computer?
I think you copied my snippet into your comment by mistake rather than whatever you found elsewhere, but regardless, happy I could help!