I have the same issue, I used inputmapper+exclusive mode to play FIFA, but now Steam doesn't recognise my controller, even when inputmapper hasn't been opened. I assume HID guardian is taking control of it on startup to get exclusive access. If anyone has a work around let me know!
I think purpose of HID guardian is to hide controller from other process except IM, so IM can connect with that controller in exclusice mode for fully emulate it to xbox360. So I don't think this is a problem. Well, I think there is a way to whitelist other apps other than IM on HID guardian, but i'm not sure.
i found the solution to this problem. uninstall hidguardian. don't just delete the folder but actually uninstall it. it will come up and tell u there is some extra stuff to uninstall. after ur finished restart ur pc and should be like hidguardian was never there. fyi, u may need a program like revo uninstaller to get it uninstalled. let me know if u have problems and i'll try to help u.
The problem is, you need HID guardian on Windows 10 Fall Creators Update for now.
I think HID guardian need to have an easy way to add new controllers & app whitelists.
Then we good to go for everythings.
Right now I play Forza a lot, and that's is a problem since Forza only support DS4 partially.
And I think newer games now support DS4. Well, if you're happy with it, that's good.
I just hope that IM gonna focus on HID guardian function, so people don't have to uninstall it.