I'm sorry to hear about the trouble you have been experiencing. There is no quick way to answer that question as one must first determine the layer in which the problem is occurring. For example, if your credentials are being rejected with a specific error then that will help determine the path (reset passwords, check configurations). If it times out, that will determine that we go another path (network down).
In any case that it is an emergency, I do not recommend waiting for our support team to answer. While our team is more than happy to offer advice and brainstorm with you on these issues, we are ultimately a self-managed provider which means that problems specific to the internal workings of your droplet will be delegated to you. In any case where you need emergency assistance and you are not certain of how to troubleshoot issues with a Linux server, you can reach out to people that do provide server management as a service. A couple of examples of these:
With that said, I can try to offer some generic advice. Assuming that the droplet can be pinged and is online, and the credentials themselves are in fact being rejected, try connecting via console to ensure that your credentials are fine:
Also make sure that you're using SFTP protocol and not FTPS, as SFTP uses the SSH protocol where FTPS is an attempt at a secure connection with an FTP server. Both of these require different back-end services, and FTP servers are not installed by default.