This is a Custom Product Form.
If you want to remove it, edit the Product and then scroll down through the settings to Custom Forms and choose No Form Required to disable the Product Form.
If you want to keep the form and fix the button (which is currently set to white text and white border on a white background) you should be able to change the colours in the Site Styles panel. This button is a Primary button. Here's what it looked like when I changed the colours to black:
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