On Saturday, one of Ethereum's largest upgrades to date, Constantinople, went live on the Ethereum Ropsten test network (testnet). One of the most significant changes Constantinople brings is the block reward reduction from 3 ETH to 2 ETH for each block mined by Ethereum miners. The Constantinople fork was slated to happen on block 4,230,000 on the testnet, but a delay stalled the fork on block 4,229,999. Ethereum core developers believed the delay was caused by miners not upgrading their clients to support Constantinople. The core developers were eventually able to ramp up enough miner support to push the upgrade through.
After the upgrade went through, another issue arose. Two of the major ethereum clients, geth and Parity, experienced a consensus failure and causing a chain split on the testnet, with miners mining different chains. As of the time of this writing, core developers are still examining the cause of the chain split, but Afri Schoedon, release manager for Parity, tweeted that because of the split, the Constantinople fork on the main Ethereum network was not going to happen in 2018.