Please deactivate all the plugins not related to the theme and switch the parent theme, check the issue, If the problem has gone, activate the plugins one by one, checking the issue to detect which one causes the problem.
They should be aligned center no matter how many items in the row.
Sorry, I found the problems. I want to share it with you. Your code has always been center, but the list content, such as ul li, in your case, u are using div class, is left. I just used justify-content: center, to make the list content center. You can see the result from the photo. Thank you for your response.
Please provide your site admin access to the private area, confirm the permit for us to deactivate the plugins for the while of checking what may take up to 15 minutes.