Problem changing slug

I’m trying to make it so that the events calendar shows up on my events calendar page.

This is where i would like it to be:

https://69.195.124.92/~theheba9/theheartofgaming/event-calendar/calendar/

However i am not able to change the events url slug in the settings to:

event-calendar/calendar/

When i try I am given the following error message:

Events URL slug must be a valid slug (numbers, letters, dashes, and underscores).

Can anyone advise on how i can allow my calendar to show on the desired page?

Many thanks

https://www.ads-software.com/extend/plugins/the-events-calendar/