All shipping classes not showing on Flat rate shipping methods

Hi there, I have set 4 different shipping classes in Woocommerce settings. All 4 show on the dropdown on the vendor’s product page. But when a vendor goes to Dashboard > shipping settings > Flat Rate, one of my shipping classes is missing from the popup box, so my vendor is not able to set the price for all of the classes. Please let me know how to fix this, thanks

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