Mouse Issues in Photoshop: Synergy Conflict

If you are experiencing trouble with your mouse in Photoshop, such as right-click not working or the paintbrush not working properly, the issue may be caused by a keyboard sharing software called Synergy.

Photoshop will work fine once you stop or uninstall Synergy.

(This is a case study: This problem happened to me once and was solved by uninstalling Synergy.)

For more information, refer to this possible reference for future.