After all leads inside the list have been dialed, the system won't dial any leads in that list until you reset your list. Resetting the list allows the system to dial the leads again if their statuses fall under the dialable statuses category. If you are using lead recycling list resets will be minimal. If you are not using lead recycling, you will need to reset your lists manually and regularly.
From the Dashboard, go to Call Center and select Campaigns.
Under Show Campaigns, Click on the Action Button and select Settings.
Within the Campaign Settings, click on the Leads tab.
Scroll down and look for Lists in this Campaign section. There are two options, Reset a Single List or Reset All List.
To check the number of leads in a list, click on Show Button 
of the list
To check the number of dialable leads in a list, click on the Calculate button. This will work for both active and inactive lists.
Note: After you click on Show or Calculate Button, the values will be cached in the system for 5 mins. Wait for 5 mins before clicking Show or Calculate Button again.
Reset a single list only, you can simply click on the word Reset for that particular list.
You have an option to reset all the lists by clicking the button RESET ALL.
NOTE: Resetting List(s) also resets the Called Count of the Leads in that List(s). Dialable leads will only calculate on ACTIVE lists.
After the reset, you will get a confirmation with the results. The leads which are still in a dialable status are now ready to be dialed again.
A pop up message saying, Resetting the List will also reset the Called Count of the Leads in this List. Are you sure you want to continue? click on Reset.
Scroll down to see the leads summary. In this section, admin can see the total number of dialable leads after resetting the lists and the reasons why other leads are non dialable.