SQL SERVER connection Time out, unable to connect (OS LINUX SERVER)

In fact, I'm not good at Linux integration. But anyway I managed it. But since a few days, I am faced with this problem. SQL Server does not connect to my application. Have an error

System.AggregateException: One or more errors occurred. (A network-related or instance-specific error occurred while establishing a connection to SQL Server.) The server was not found or inaccessible, verify that the name of the server was not found. instance is correct and that SQL Server is configured to allow remote connections. (Provider: TCP Provider, Error: 40 – Can not open a connection to SQL Server) "—>

I am very worried about my data which is very important to me. I've also checked the name of the instance and the password, which is correct.

When I try to connect with SQLCMD
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when trying to run dotnet WebApp.dll
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What I've found is that the SQL Server services are down. I have tried to restart several times but I have not worked. Also tried to search everywhere even I complained about the digital ocean. But did not get an appropriate answer.

Even I do not have backup of my database.