You cancelled on InstagramNetworks reads: you didn't grant the permission on Instagram, so nothing was connected. Nothing was saved on either side. Press Connect again whenever you want.
Instagram stopped the authorizationThe message reads: Instagram stopped the authorization. Try again. Usually a half-open Instagram session or an extension breaking the return. Retrying is safe.
It authorized but was not savedThe message reads: Instagram authorized it but we couldn't save the account. Try again. The permission was granted on Instagram's side and nothing was written here, so starting over does not leave two connected accounts.
You took too longThe message reads: the connection took too long and expired. Start again. The trip to Instagram is valid for ten minutes, so a tab left open needs a fresh start from the button.
The token expiredNetworks says the token expired and scheduled pieces won't go out. The way out is Reconnect, the same button as the first time: Instagram does not renew a permission that already expired.
Your account is still personalInstagram will not offer the publishing permission and you come back with nothing connected. Switch to professional and press Connect again.
The button is greyed outDirect connection is rolling out per account while Meta finishes reviewing our app's permissions. A grey button means yours is not enabled yet: until then, use the token path below, or download the piece and upload it yourself.
Test connection does not return your handleThe id and the token have to belong to the SAME account. The usual mistake is copying the token from one account and the id from another, or generating a token without both permissions. The red line under the fields is Meta's own answer, so it says what was rejected.