Bluetooth mouse not connecting at wakeup

My bluetooth mouse is not connecting when my MacbookPro wakes from sleep, while it used to do so. Each morning when I get to my office I connect my Macbook to my Thunderbolt monitor. The computer wakes from sleep with keyboard strokes, but the mouse does not connect. Connecting the mouse requires manually doing so from the bluetooth menu, which can be done by either opening the Macbook and using the track pad, or by connecting a USB mouse.

This behavior started within the last month. Prior to that, the mouse was autodetected just fine.