you need to explain a detail what problem did you experience. People will only use their own assumption about whats your problem with
MEW error can not see the history of my wallet when I've been using the private key, if you can explain why it happened and how to solve it? And what do you think about cold wallet, is this secure for me?
MyEtherWallet error maybe it because of the phishing site honestly I did not encountered error like this maybe it because of internet connection. You need to be careful next time and avoid using mew in browser it might be risk.