If you want to use the new Block Widgets screen, you need to do a little more debugging. Your theme (most probably) or one of your plugins conflicts with the new widgets editor.
In order to see what is the source of the problem, please attempt to
- disable all plugins
and
- switch to a default theme (Twenty Twenty-One)
If the problem goes away, enable the plugins one by one to identify the source of your troubles.
As an alternative, if you want to make these changes only for your eyes, without affecting normal visitors to your site, install Health Check Plugin
1. Under Tools > Site Health, on the Troubleshooting tab, click on the Enable Troubleshooting Mode button to disable all plugins and change the theme to a default one (just for yourself, while you’re still logged in).
2. Then, by using the options displayed at /wp-admin, you can turn on/off plugins and themes, one at the time and check what plugin is the cause of your problem.
3. Don’t forget to Disable Troubleshooting Mode when you’re done. And you can also uninstall the Health Check Plugin to keep the plugin list clean.
After you see where the issue comes from, you should contact that theme/developer author and ask them to update their product.
I understand this can take some time, but this way, you can make use of the latest features and also help others by asking the developers to update their product.
Kind regards!
