Transferring Game Centre game levels

Just purchased new Ipad Mini version 6 Transferring from Version 5. Game Centre signed in on both old and new ipads using same Apple id. Game Centre is not showing same level of game on new machine but asking if I want to update to level and warns that this will delete current date. Would have expected it to show same levels across both machines without updating. worried that I will loose levels which we have been playing for 5 plus years. It looks as if Game Cetre is not synching