I've just bought a weather station. German make.
It has come with no UK electrical plug. Is it legal to sell goods in teh UK without necessary adaptor?
It is illegal to sell electrical items in the UK without a plug (brought in for safety reasons).
However,as you bought this from an Amzon Marketplace seller (who I would imagine is abroad) then you would not be covered.
I would apply to Amazon/seller for a return/refund as it doesn't work in your country,and just be more careful in future?