@Oradainer I had this same issue, I had to run this part of the command in step 5:
protontricks -s Ascension
This gave me the ID of the application (note, this is a fake ID, run the command to get yours!)
Found the following games:
Non-Steam shortcut: Ascension (1234567890)
To run Protontricks for the chosen game, run:
$ protontricks APPID COMMAND
NOTE: A game must be launched at least once before Protontricks can find the game.
Then run the second command but replace $gameID with the ID that the command above gave me, like this
protontricks --no-background-wineserver 1234567890 dotnet472
Then it started to install .NET 4.7.2, which I clicked through to finish.
Thanks @drkalle for the guide, it helped a lot to get things working flawlessly. I would suggest linking to the app image download page in step 2, I didn't know that existed until I dug some, but I am new to Ascension.