I am with coinbase for several years. I am fully verified user. As we see BTC is now at ATH for this year, my plan was to sell the btc now and buy back later. Before doing that I was planning to bring some more BTC from other exchanges in coinbase and then sell all together.  After transfer is completed I was ready to sell.

But before that all on a sudden yesterday coinbase sent me this status " Account under review Your account is currently being reviewed and we need some time to verify your info. During this review, you won't be able to use Coinbase. Reviews generally take a few days, so sign in every day or two to check your status."

I am fully verified so, no idea why on earth they are doing this. I sent them email and got a copy past reply!  If you remember coinbase did similar kind of things on last bull run on 2017 when their webpage was just went down at the time when BTC was hitting $20k. I couldn't cash the opportunity back then because of this. Now in this bull-run they are doing so called 'Review' out of no where and hold my account. I can't buy/sell, or even transfer my btc to other exchange! No sure if coinbase is intentionally doing this during Bullrun!

I am fade-up with coinbase and will transfer all my balances to another exchange as soon as it is sorted. 

I just thought I will  make everyone aware of this so that you also don't fall for this crap at time when you need to sell/buy to grab the opportunity.

Why not store your btc in a wallet that's not an exchange and when you need to trade or sell, you'll transfer the sum you want to sell into the exchange website. That is safer.

Try tagging them somewhere other than their customer support? Idk if they have a twitter or Facebook, but you can try looking out for them. Even an email could be tried. Well, even with that they won't answer, I guess you can't really do anything about it, they have your wallet locked after all. Possibly trace the coins that came from your wallet that was sent somewhere else, coinbase might, just might, have seen something odd or weird in the recipients, and if yes, well you can coordinate with them to speed up the process.

The lesson learned is not to use coinbase as a wallet, or any other exchange for that matter. You can just use it as a medium to buy and sell your coins, but after that, immediately move it to your non-custodial wallet so that no one can actually lock you out of your funds.

Why not store your btc in a wallet that's not an exchange and when you need to trade or sell, you'll transfer the sum you want to sell into the exchange website. That is safer.