Generate “never-expire” access token for Facebook Page

Question

I have managed to post to Facebook Page via API (C#), but when administrator of the page logs out, the following error occurs:

\"(OAuthException - #190) Error valida

Answer 1

1. Create an app if you don't have - https://developers.facebook.com/
2. Create a short lived user access token in the Graph Explorer - https://developers.facebook.com/tools/explorer/

Select your app created above and select “Get user access token in the drop down”

In the user access token pop up you can select some permissions for the token. For an non expiry page access token you need to select "publish pages" and "manage pages"

3. Create long lived user access token

Go to https://developers.facebook.com/tools/accesstoken/. There you will find short lived user access tokens and app access token of all the apps you have

Press debug option of user access token of the app created above. This will take you to the debug tool. Where you can find all the information of short lived user access token.

In the bottom there is option to generate long lived(60 days) user access token for this short lived user access token. Generate long lived user access token by selecting “Extend Access Token”

4. Create never expired page access token

a. Go to the Graph Explorer - https://developers.facebook.com/tools/explorer/.

b. Paste the long lived user access token generated in previous step inside “Access token” field.

c. Access “/me?fields=access_token” api . This will result page access tokens and pages related to them. These page access tokens will never expire(until user change the password/user revoke the app)

5. Verify non expiry page access token

a. Go to https://developers.facebook.com/tools/debug/accesstoken/

b. Add the page access token retrieved from above step into “Access token “ field and debug

You will get expires as Never

Found here with little changes: https://medium.com/@Jenananthan/how-to-create-non-expiry-facebook-page-token-6505c642d0b1