When you first connect a new inbox into Uptics, under any User account, Emails will only sync moving forward after the time of connecting the inbox inside of Uptics.
For inbound emails (replies to existing threads or new emails from your contact records) to show up and sync inside of the Uptics Inbox, the email address of the prospect sending you the email must be present as a contact record (people or company) inside of Uptics.
If a contact you emailed directly from your email provider (i.e. Gmail or Microsoft and not from Uptics) replies to you, and they are not a contact record inside of Uptics, the reply or email response would not show up inside of Uptics.
New email replies will only show up under the Uptics User Account that the particular inbox that received the email reply is connected to. These replies will show up under the specific User's Sales Inbox.
So, for example, if John Smith has the inbox [email protected] connected under his user account and gets a reply, then only John will see this new reply notification under his account. Jane Smith, another user under John Smith's account, will not see this reply come through under her specific Uptics account because she doesn't have the inbox connected under her account.
The Inboxes or WarmUp pages will allow you, as an Admin, to run filters on your different Users to see which inboxes are connected under which User.
If you are not able to see an email reply from a contact inside your account, you would want to check and make sure that the particular contact record is present within your Uptics account, and that you are under the correct Uptics User account that the connected inbox is associated with.