HarkMahlberg, rok temu (edited rok temu)

From everything I can see, you did have to buy games on Stadia. They would give you a free game a month, but if that wasn't the game you wanted to play, you had to buy it. The base version of Stadia was free, but the Pro version gave you a discount on games - it did not make them free.

This is the official support forum and there are many Q&A's about purchasing games:

https://community.stadia.com/t5/Payments-Billing/Can-t-buy-games-in-the-Store-OR-HDT-01/m-p/52482

Got my Stadia Pro account with a credit card...

... If you have an Android device, you can also try via the Stadia app to purchase games (once purchased, you can play them everywhere, on mobile, TV or PC).