There's no way to re-activate social connect created via another app. EasyAuth Social Login app allows to login via social network for customer who created account via our app only. It was developed this way because to log customer in automatically our app has to set one-time password for their account. That's only approach possible with Shopify (except on Shopify Plus). If we'll do that for account that was created manually (with login and password), customer won't be able to login with his password anymore, so it will be very confusing for your customers.
In other words, you may just remove those accounts, and then customers will be able to login again via our app. But you may lost some accounts if they won't login again. Otherwise, they will get error message that they already have an account, but should login with their email and password.