Hi,
Directory Opus dissapears from my computer at work. Bitdefender endpoint detects dopus.exe as malaware and delete the application 
It now whitelisted but I can reinstall it. I got this error message, even when launching the setup in admin mode.
(dopus was replacing explorer on my computer)
Any idea ?
I'd say you need to talk to Bitdefender support as it sounds like it's still interfering even though you have it whitelisted.
Do not know whether this will help, but I had a similar problem a few months ago with another program - NOT DOpus.
In the end I had to remove Bitdefender completely using their special uninstall tool.
https://www.bitdefender.com/uninstall/
Then I re-installed the offending program before re-installing Bitdefender and checking that the offending program was whitelisted.
No troubles since. Guess the uninstall tool clears all the Bitdefender detritus from the registry.
Nevermind, after a few reboots I could reinstall dopus 
Why would you do that? 
Haha In my case it's my company laptop, I don't have the choice, I can't even close Bitdefender 