If you find that the toilet flush trip lever, or flusher, isn't working, the fix could be as simple as a chain or nut adjustment to the lever. If the lever itself is broken, then replacement is a simple 20 minute job with a replacement lever for less than $10. In the video, we are using an adjustable lever which must be carefully bent to the correct angle before installation.

Link for a similar lever:
https://www.homedepot.com/p/Fluidmast...