I work for ThinkForex and after speaking with clients gathered some workarounds (link at the bottom)
If you have tried everything in that link - the final suggestion is to contact your IP provider and ask them to reset your internet connection.
When this also failed to work for another client, they went out and bought a new modem - then was able to log in. I wish I could give you all a solution that definitely works, but after a week working on this with clients, still left scratching my head...
The really odd thing is only some clients were effected, whilst others were able to trade as per usual, on the same server. It was also strange how different solutions were required for different clients - what worked for one person would not work for another! To make it more confusing I was able to log into clients MT4 accounts whilst they could not - this all points towards some conflict with the users IP address. A few VPS users had been told by their provider that ThinkForex had blocked their IP address - this was certainly not the case.
MetaQuotes have been working discreetly in the background, reluctant to admit there was an error - this is infuriating for all involved (Traders, Brokers, Liquidity Providers).https://support.thinkforex.com/index.php?/News/NewsItem/View/24/london-live-server---metaquotes-build-issue
"The game of speculation….is not a game for the stupid, the mentally lazy, the man of inferior emotional balance, or for the get-rich-quick adventurer. They will die poor.’ Jesse L.Livermore:Reminiscences of a Stock Operator’,1923