Land purchased but registration being denied. What can be done ?

Sir, my dad purchased land but registration not completed due to some land tax issue.( Land tax not paid from many years). Regular follow up done but they use to say we will do it after solving tax issur and we trusted them as relatives and they were in financial problem.After 15 years dad contacted many people and cleared the tax problem and now fresh papers came with their name from whom we purchased the land. They denying to register the land by our name. We got four bond papers signed by them saying that all amount is paid and will do registration after solving land tax issue. We got home opening pics our marriage pics where they were also present in the functions. I don't have legal registration papers but can I file case on them. And what are the chances of winning the case