If you created a new event and want to reuse the URL from an old event, do it this way.
Go to the old event from which you want to reuse the URL.
Click on `Settings`
Click on `Setup`
Click on `Domains`
If you have another URL entered as Redirect address
Click on the Redirect address
Click on `Make primary`
If you do NOT have another URL entered as Redirect address
Click on `Add domain`
Enter a new domain
Click on `Save`
When a new domain has been added
Click on the domain you want to reuse
Click on `Delete`
Now, the domain has been removed and can be added to the new event page.