I tried to enable Facebook Insights for my web. I added my page's APP_ID to fb:admins to enable every admin of my page to access Insights when logged into Facebook as Page. But when I try to save the dialog message appears:
The app ID "123,123,123,123,123" specified within the "fb:app_id" meta tag was invalid.
I double checked my app ID and it's correct.
To link Domain Insights to an app rather than a user, you need to use the fb:app_id tag:
<meta property="fb:app_id" content="your_app_id" />
Only personal IDs are allowed in the fb:admins meta tag. Application IDs won't work, even though they are actually valid (in contrary to what the error message says).
Optionally, it may also work with page_id:
<meta property="fb:page_id" content="395450240451647" />
The suggested app_iddidn't work at all :(
You have to make public you app to start works.
error invalid fb:app_id is sometimes misleading. The account you are using to test this needs to be added into test users list of facebook app. Or try to test using the admin account.
Sometime your facebook information already crawl by facebook and it will be cache
You need to clear there cache to test again
You can access this link : https://developers.facebook.com/tools/debug/
paste your clink you want to test
Click Crawl again
来源：https://stackoverflow.com/questions/13347937/the-app-id-specified-within-the-fbapp-id-meta-tag-was-invalid