Hi,
I don't know if you developed this app, but the way the app is structured and the fact that it is calling non maintained libraries (ShinyBS) make it hard to debug.
I can help you create an app with the same features but with the latest libraries for the themes etc to make it work, and make the code more clear and easy to understand.
Please, feel free to contact me over chat.
PS : As it seems you're from France, you can directly talk to me in French :)
Best regards,
Naly