VAT Flat Rate Scheme - reclaim VAT on large asset purchasses

SUGGESTED

Hi

We are now registered for VAT wef 1 January 2021 on a flat rate scheme. In 2020 (previous financial year), we purchased 2 vehicles, and my understanding is that we can reclaim the VAT back of the vehicles at 20% with our first VAT return - due by May 21. The SAGE guide says to tick the box that identifies the asset as outside the flat rate scheme, however I then get an error message stating I cannot do this given there is a different VAT scheme in place... In settings, I have the correct entries. Does anyone know where I am going wrong - or should I manually amend the VAT return when I come to complete it? I would appreciate any advice or guidance please. 

Many thanks

James