IMPORTANT:
This guide (blockchain fix) only works if you have followed the Masternode Quick Guide. Personal configurations are not considered in this guide.

### Stop your BitCore Daemon
bitcore-cli stop

### Remove Data
cd ~/.bitcore
rm -r blocks/ chainstate/ indexes/ sporks/ *.dat *.log .lock masternode.conf

### Download, Extract and Copy Bootstrap Files
cd ..
apt install unzip
wget https://github.com/LIMXTEC/BitCore/releases/download/0.90.9.1/z_bootstrap.zip
unzip bootstrap.zip
cp -r blocks/ chainstate/ .bitcore/

### Start your BitCore Daemon
bitcored -daemon

### Check Headers and Block Height
bitcore-cli getblockchaininfo| grep -i "headers" -B 1

### Compare your Blockhash
bitcore-cli getblockhash 590067
must be identical with ---> 0c3bfcb6c59416a6f9906222fc7d3a354825976aea7e1002b133c20c7a443859

### Check Masternode Sync
bitcore-cli mnsync status

and wait until these values are "true"

  "IsBlockchainSynced": true,
  "IsMasternodeListSynced": true,
  "IsWinnersListSynced": true,

Now you can start your Masternode from your BitCore QT Wallet.