Property tax assessment

I bought new flat in 2018. Occupancy certificate has been issued in Oct 2017 for the apartment. Till date property tax assessment is not done for the apartment. Builder is saying he can support us if all the flat owners come together with requisite details for which everyone agreed except one flat owner. That particular owner is not agreeing to the charges of builder for getting the work done. On the other side builder is saying without all the owners property tax assessment cannot be done. What is the solution for this? All the flat owners paid the charges to the builder except one owner.