Cannot add new variations to existing products

Hi! I have just discovered a problem. I am trying to add new variations (new fabric types and sizes) to an old/existing product. Every time I attempt this the product shows on the website as “Sorry this product is not available”.

If I delete the new variations that I attempted to add, the product then goes back to showing as available with no issues.

This has never happened before? I need to be able to add new variations to my products regularly, is there something I am missing that I should be doing or is this a Glitch with the new update?

(Using the updated version of both Word press and Woocommerce)

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