[Updated 2023] How To Fix Purchase Button (Family Sharing)

Sad truth, but thx.

UPDATE!!
I was mistaken. Purchase button can appear for other reasons too. Steam is using this to show some type of error, not telling explicitly which one. I have noticed that some games work and can be played but at other times they cannot be. There are a couple fixes that I have found to work:

1. "I think you might need to have your friend log into Steam on your Steam Deck so you can re-enable Family Sharing on that device. I had this issue too, until I realized that I never had my friend log in to my Steam Deck like I had them do on my Windows PC- so my device was never actually authorized to share their library. After having them log in and check my device in the Family Sharing settings, I haven't had much trouble getting the games to work."

It is an issue with Steam syncing with their servers. It displays Purchase button because it has saved previous state but forgot to update it.
The fix that could also work is:
Go to Steam -> Settings -> Family -> click on Manage next to Family View -> click ALL GAMES and click Next -> Next.

Restart Steam after each fix!!

thank you, i always thought there is something wrong with my steam account, unfortunately my game isnt sharable :/

Which game are you trying to Steam family share?