We have updated our Community Code of Conduct. Please read through the new rules for the forum that are an integral part of Paradox Interactive’s User Agreement.
You are using an out of date browser. It may not display this or other websites correctly. You should upgrade or use an alternative browser.
I haven't had any issues on my Linux machine, running Ubuntu. Start with trying to verify your files. If that doesn't work, completely reinstall the game, by also removing the "Documents" folder (but do remember to backup your save games!).