If you are being advised to contact Support whenever you attempt to log in on your account, the most likely reason is that you have been banned from the game. There are a number of reasons why this might be the case, which I'll outline below:

Toxicity

We at Bytro take a firm stance against toxicity and harassment. Our games are intended to be enjoyed by everyone who plays, and we will not tolerate any behaviour that would damage the experience for other users. This means that abusive content sent in diplomatic messages or posted to the Newspaper may result in removal from the match in question, and if the behaviour is repeated, a permanent account ban is possible.

Metagaming

Using multiple accounts, dedicating your nation to helping somebody else win at the expense of your own chance of victory and unfairly ganging up on other players outside of normal diplomatic circumstances would qualify as Metagaming and may result in action taken against all involved accounts.

Payment Issues

If a recent payment that you have made has failed for any reason - such as insufficient funds, a technical problem or a chargeback - then your account will be suspended until the purchased Goldmark or High Command can be removed from the account. These suspensions are automatic and temporary, and will be removed as soon as one of our agents removes the purchases from the account.
You do not need to appeal this decision, as we are notified when the suspension occurs.