The main issue is the disputed Nagorno-Karabakh region, internationally recognised as part of Azerbaijan but controlled by ethnic Armenians.
The fighting over Nagorno-Karabakh escalated on September 27. Each side has accused the other of targeting civilians. Both sides have rejected talks and ignored growing international calls for a ceasefire.
https://www.neweurope.eu/article/pompeo-criticizes-turkeys-involvement-in-nagorno-karabakh-conflict/