If one of those kinds of programs blocks a game it will cause the game to not load or crash when loading. The last thing i can think of is checking whatever anti virus or anti malware software you use and make sure its not blocking the game. You could try a complete re install of the game. Sometimes its exe files or redistributeables that are supposed to go in during the install dont. wait for it to finish and it should tell you after its done validating if you're missing any game files that failed to load in during the install. You could also try going to the game in your steam library, right click on stellaris, click on properties and then go to local files and look for something along the lines of validate integrity of game files.

As for some reason the game forces you to be logged into your paradox account in order to run the game and then from that launcher is how you actually start up stellaris. Some options you could try is for one making a paradox account if you dont already have one and the game hasnt prompted you do so yet.

How to play stellaris on old laptop