I had a similar problem only yesterday with a RBSXT-5HacD2n when I did a RouterOS upgrade. What finally worked was using "netinstall".
Remember that for netinstall, you need to disable Windows Firewall and run netinstall as Administrator or it's likely your device won't show up in the list.
Best to Google for detailed instructions but here are some to get you going:
Normis' definitive guide on how long to hold down reset button for different boot functions:
One of many step-by-step netinstall procedures (although doesn't mention run-as-administrator or correct reset button timing):