Unable to get my app working on my localhost

Hello everyone,

I do have a dash app working on my Windows machine, on localhost. I also do have an app running on a Ubuntu VPS.
I’m currently trying to deploy my app on a laptop, on which there is Ubuntu 18.08, same version as on the VPS. Dash is up-to-date, and all the dependencies are up-to-date too, even though I dont need them immediately.

I’ve copy-pasted the code from the “Getting started” section, into my Pycharm editor; in other word, my app couldnt be simplier.
When I execute this code, it runs error free. At least in the pycharm console.

However, on my localhost, there is strictly nothing. Firefox only displays “waiting…” forever. Does anyone have a clue regarding what’s going on?!

OK, fixed: for some reason, I used to copy my code, and paste it in the PyCharm Python Console. This didnt work.

But if I run the script from a terminal, it works: I can reach my app on localhost.

I must be missing some knowledge on the difference between these 2 ways of running a script. If anyone could enlight me on the matter, he will be welcome !