Symptoms
There are no Queue Newsletter button at Newsletter Templates page in Magento backend. Queue Newsletter button is used to queue newsletter messages and it is not possible to send any newsletter in Magento when Queue Newsletter button is missing.
Cause
The most probable reason is disabled Email communications at System > Configuration > Advanced > System > Mail Sending Settings.
Solution
Please ensure that Email Communications are not disabled at System > Configuration > Advanced > System > Mail Sending Settings: