In analyzing over 4,500 support tickets over 2015-2017, it was pretty clear that the #1 source of confusion in using the Candid platform was ensuring that the right brand account is connected to your collection.
In the vast majority of cases, users were signed into Instagram.com under a personal account and so when using the "Sign In With Instagram" option on our login page, they would be immediately redirected back into their collection with the same "access_token" expired error as before.
The classic remedy has always been to sign out of Instagram.com first before using the "Sign In With Instagram" option.
As of Jan 2, 2018 we have now improved the Instagram login experience so that it prompts to you to explicitly select the identity you'd like to sign in with. We're rolling this out gradually throughout the platform but you'll start to see it today on any reconnect notices that appear within your Candid dashboard.
You can also try it out directly here: https://www.getcandid.com/account/instagram/?forcePrompt=true
This should result in a lot less confusion for community managers that are managing multiple collections on Candid.