Alt + P cannot work because it's the default shortcut from Windows

[kanlukasz]

When you click Alt + P on a Windows computer in Polish, a menu will open.
This is because the letter P mean Plik, which means File

My env:

1. Windows:
   

2. Firefox:
   

[jbhoot]

Yeah the default shortcut is quite insensitive to non-English users. Sorry about that. Luckily Firefox lets you modify the shortcut for any addon.

Find the setting here: