do you find any resistance while trying to click on it(physical resistance) if yes it could be that the trackpad needs to be replaced or maybe like how few people found their swollen batteries to be the cause of the issue.
However first ensure the track pad is clean then ensure all settings are proper. If all this doesnt help you could do get into recovery mode by holding option key right after you hit the power button. while there check if you trackpad is functioning fine if it functions fine then its a software issue needing you to reinstall if not take it to apple for a diagnosis they charge around $40 to diagnose, incase the trackpad is faulty it would not cost much to have them replace it. If the cost is out of your budget then do get an external mouse/trackpad.