Permalinks don’t update nor link properly

How are you linking to the other events?

Are you hard-coding the anchor links somewhere, like in your post content or custom fields? As in, are you typing out <a href="https://wordpress.stackexchange.com/questions/327355/example.com/?p=123">? If so, you might have manually update all of the links you added to use the new permalinks.

After you updated the permalink settings to %postname%, are you seeing the correct slug on regular pages and posts? Or is it still showing the default ?p=123?

For WP Events Manager, it looks like you might need to also add some custom code to your functions.php file to get the URL structure to work the way you want it to:

https://www.wp-eventmanager.com/documentation/changing-event-slugpermalink/