Hi there, have you updated WordPress recently? What changed just before the widgets stopped working?
I would advise if you have then to try disabling the third party plugins, as it could well be one has a conflict since the update. If so then make sure the plugins are all up to date, and turn each one on/off to see which is causing the problems with the widgets. Once you have the plugin causing the problem, check with the plugin developer to see if a new one is available or if they can offer a workaround.
If not, then it could be child theme, what’s customizations are in the child theme? Any custom scripts or codes? You can test if it’s the child theme by switching to the main theme and then seeing if the same problems occcur and then back to the child theme.