While many people have no use for this guide, I recently had a bootloader issue and nobody seemed to know what to do, in fact, steelseries' own help page is horribly outdated and has links to pages that no longer exist, so I thought I would post this in the hope that I can help people in the future. I had the issue with my steelseries sensei, but this should work for any peripheral.
Note: I did all of these things, and I am not 100% sure if any of these are not needed. Also, I did this to fix the bootloader not found issue, however, this should work with just about any issue as this completely re-installs everything. You will need two mice for this, your steelseries one, and another one to navigate while that is not usable (that is if you are fixing a mouse, if you are fixing a keyboard have two of those, ect.).
1. Remove all steelseries software from the computer (Engine, firmware updater, ect.) Note: if you have both steelseries engine 3 and steelseries engine 2 (just called steelseries engine) just remove the one that pertains to what you are fixing
2. Make sure there is no steelseries software running (task manager > processes) if there are any, hit end process
3. Plug in your extra mouse/keyboard, then remove all outdated drivers from old products (this is a good thing to do anyway) (device manager > view > show hidden devices, then go down to mouse/keyboard and right click > uninstall do this to all the old drivers), also uninstall your steelseries mouse/keyboard (I was able to tell my two mice apart because my spare had power saving settings, but the steelseries did not (as it was not fully functional), also, old mice will be grayed out, connected ones will not be)
4. Turn the computer off, then plug in the mouse/keyboard
5. Turn the computer on
6. Let windows do its thing for a little while with the drivers (it will probably fail, mine did)
7. You should now have at least some functionality with the mouse (can move it and click, but maybe not use scroll wheel/click and drag), if you have full functionality that is fine
8. Download the steelseries engine
9. Go through the installer, it will ask you to update firmware, say yes
10. You should now have a fully updated mouse/keyboard that is ready to game!
Again, this guide may be useless to a lot of people, but if even one person can save themselves the 2.5 hours of troubleshooting I had to go through, then it is worth it.
