Step one: Make sure overlay is turned on



Step 2: if your discord doesnt find the game you want go to game activity and add it.

Step 3 (Activate overlay for the newly added game or for whichever game you just added)

1st screen is the global settings for overlay
some games are not detected by discord. Use the last 2 screenshots to add it to discord.
Make sure that everything is properly set
And sometimes running programs in admin mode blocks discord. (your millage may vary on that)

hope this is helpful for some