This bug has existed since the dawn of time.
Please Stardock, do something, that's ridiculous.
Also, make sure that the research points and the word "Research" do not overlap at the bottom left of the screen.
Edit: Save: https://drive.google.com/file/d/1MuPiDaXrYcX89zeOzCtEsoY0tag0_p68/view?usp=sharing
Go to the Ideology Screen.
Choose "Slavemasters" (Greed IV) and unlock it.
Then "Research Complete" screen is displayed, click on "Next" and "Choose New Tech" buttons.
The Research screen is opened and you can also see the tech are gray in color.