Magnetic link does`nt work suddenly. Anyone knows why?

Explain how?
Are you copy-paste into ADD dialog of Tixati?
Are you using your browser?
If you are using browser you need to make sure it OPENS with Tixati. If you changed your version of Tixati, you may have lost the associated program.
From there you can also check if Tixati is set as the default handler in SETTINGS Shell Integration