Simply go to ‘Customize.’ Such as dashboard – appearance – Customize.
Then go to the Menus, then Main Menu, and find the menu item you don’t want to display. Expand it. And click on “Remove”. It doesn’t remove the page but the menu item in the list displayed.
This is probably a WordPress error and not a Pinboard error.
Go to your Dashboard – Settings – General and select a “city” for the timezone. Don’t try to select from the numbers but find a city in your timezone and select from that.