Hi @Rasha212
This topic has been discussed on here quite a lot recently .it's to meet new government digital regulations to try and clamp down on those not declaring their income when selling online.
Your accountant is the best person to advise you on this. Often there is dual taxation and you pay tax in the country you immigrated to and in the country where the money is earned .
Your profile lists you as living in the UK not living elsewhere hence why you were sent the request .