ERROR: failed to create quartz event tap

Solution 1: Try to remove local config and restart synergy
⚠️ Warning: serial-key lisence will be asked again.
*Prepare your liscence key before run those commands.

# Open Terminal
# Run commnad bellow and restart synergy
rm ~/Library/Preferences/com.http-symless-com.Synergy.plist
rm -rf ~/Library/Synergy/
killall -u $USER cfprefsd

Solution 2: (MacOS Catalina / Mojave)

Goto System Preferences > Security & Privacy > Accessibility
Then Remove synergy 
And Add synergy again
And Reopen synergy

MOUSE LAG

Problem : Wifi network 
Solution Try Turn Wi-fi off and on
Then Try synergy again

Reference
https://sourceforge.net/projects/synergy-stable-builds/
https://members.symless.com/forums/topic/3064-the-executable-could-not-be-started-although-it-does-exist/
https://members.symless.com/account
https://symless.com/help/articles/s1-mouse-cursor-lag