Changing a page URL: can't do it….

When editing a page, I try to change the URL of the Permalink from https://example.com/wp/welcome-2/ ?to https://example.com/wp/welcome/ – I click the OK button but the page URL reverts to welcome-2

I had previously deleted a page that probably had the URL https://example.com/wp/welcome/ – is that the issue?

If yes, what do I need to do to rename the page as desired?

Thank you!