Your Suggested Amounts section is set to Show, but the buttons are not appearing on the form.
NOTE: The Suggested Amounts section and buttons cannot be used in conjunction with a Calculated element (Derived Amount). In other words, the Suggested Amounts section only functions with forms that do not have a custom calculated formula.
Check your form's configuration for a Calculated form element (Derived Amount) that is calculating the final donation amount. This type of calculated element effectively replaces/overrides the Suggested Amounts and default donation box.
If you wish to restore the Suggested Amounts buttons, set your calculated element to "Hide" in order to revert to the default/suggested amounts. The form will no longer calculate any custom elements for the total amount, only what is selected or entered within the Suggested Amounts section moving forward.