Hi Upwork support,
I got the same problem too : while entering my french VAT number, I have message about "unrecognized format". Could you please help ?
Have you checked if the VAT number can be validated on the VIES website here? If it does and you are still having problems adding it to your Upwork account, please let us know so we can assist you further. For more information about VAT, you can check out this help article.