The old staking contract has be deprecated.
The previous implementation of staking was called Staking v1. Staking v1 was launched in September 2020 and required users to lock up MTA for a pre-selected time period, ranging between 1 week and the end of September 2021. In return, users received voting power and reward earning power based on the weight of their MTA in the staking contract, as well as on the select lock-up period. Longer staking periods provided higher staking returns, higher MTA rewards boosts and higher voting weights.
The application can be still used to claim rewards and to withdraw from Staking V1:
Staking V1: staking/claim page