The visibility and availability of conversations and SMS/MMS messages depends on channels (lines) settings and selection. It is also possible you have blocked some numbers from receiving messages.
Some or All Messages (or Conversations) Are Not Found
When this happens you need to check the SMS Text Channels MANAGE PHONE NUMBERS option in the TeleConsole settings and ensure that at least one of your SMS channels (lines) is active!
If you switch off all the channels you will not see any prior messages. If only one channel is active you will only see the conversations previously received on it.
If a channel is inactive you are still receiving messages for it. These are stored on the Telebroad server and become accessible as soon as you activate it.
Messages Are Missing In a Conversation or not Being Received
In this situation you can see all your conversations, but you notice that some messages are missing inside the conversation themselves or you cannot receive new messages for a conversation even that the sender confirms he messaged you.
This happens because you have changed the SMS line you are using for sending a message from the drop-down menu at the top of the conversation you opened.
When you do this the content of conversations is affected and only messages delivered to the selected line will be shown at any given time!
To fix the problem simply select the line you originally used for starting the conversation or to receive messages for.
If you have the correct SMS line selected but still can't receive new messages for a particular number it is most likely you have blocked the numbers from receiving SMS messages.
Blocking numbers is usually done to deal with SPAM messages, but it is possible you may have blocked a number unintentionally.