Below script will help you to kill all the existing connection coming to the user databases.
Copy and paste the script in Query window and change the DBName to the one that you want to troubleshoot.
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DECLARE @DatabaseName nvarchar(50)
SET @DatabaseName = N”
DECLARE @SQL varchar(max)
SET @SQL = ”
SELECT @SQL = @SQL + ‘Kill ‘ + Convert(varchar, SPId) + ‘;’
FROM master..sysprocesses
WHERE DBId = DB_ID(@DatabaseName) AND SPId @@SPId
EXEC(@SQL)