TE Boot not appearing


First time poster here, so please excuse me if the issue has already been addressed.

I’m having trouble with my old trusty OP-1 (had it since 2012) - I wanted to update to the newest firmware and to my surprise, the TE Boot menu does not show up. The speaker click is audible, so the unit is alive, but the boot menu does not show up. On the other hand, when I power up the unit normally, everything it works fine.
I exchanged a couple of emails with TE support, but their proposed solution didn’t work (they provided me with a te-boot.op1 file and instructed me to copy it onto the device in disk mode, but the unit does not react to any file put in the root directory and just goes back to tape mode upon usb eject) so they referred me to a service center.
Now the reason I’m writing this is that I would like to ask if anyone here had a similar problem and managed to overcome it on their own? Can it be done at home? (I lack the technical skills myself, but I know a guy who most definitely would do it - if it’s doable at all)