PowerShell issue when using string variable from web.config in concatenation - powershell

Question

I have this issue with a string ($dataBaseName variable) I'm pulling from a web.config file via a function.
When I Write-Host it displays the value, and when I use GetType() it shows that it is a System.String, but it will not pull the value when concatenating with another variable. Eventually, I want to use it as a parameter to call from the module I'm writing.
Here is the code I use to get the $dataBaseName variable I'm having trouble with.
# Get WebConfig Detail
$configPath = Get-ItemProperty 'HKLM:\SOFTWARE\Wow6432NodeItem\Key\Settings' `
| Select #{Name="Path";Expression={$_.installPath + "\Item\Web.config" }} `
-ExpandProperty Path
$config = [xml](Get-Content $configPath)
function Get-WebConfigKey($key) {
$config.SelectSingleNode("//appSettings/add[#key='$key']").Value
}
# Set Database Variable
$databaseName = Get-WebConfigKey "databaseName"
Later I try to reference it by combining it with the computer variable using many different ways to concatenate it using (with (), string.format, etc.), but it will only display "ComputerName\" for the value of the $instance variable.
$computer = Get-Content env:computername
$instance = $computer + "\" + $databaseName
If I hard-code the database name it works fine.
$instance = $computer + "\" + "exampleDatabase"
I'm using the information to an SQL query as below. I'm actually going to use a secure string for the password later, but this is for reference.
$computer = Get-Content env:computername
$instance = $computer + "\" + $databaseName
$server = new-object ('Microsoft.SqlServer.Management.Smo.Server') $instance
$server.ConnectionContext.LoginSecure=$false
$server.ConnectionContext.set_Login("sa")
$server.ConnectionContext.set_Password("examplePassword")
$db = $server.Databases.Item("Maduro")
[String] $sql = "SELECT SomeRow FROM SomeTalbe;"
$result = $db.ExecuteWithResults($sql)
$table = $result.Tables[0]
foreach ($row in $table) {
$someVarible = $row.SomeRow
}
Web.config excerpt:
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<appSettings>
<!--NEXT GEN EF DB INFO-->
<add key="providerName" value="System.Data.SqlClient" />
<add key="serverName" value="LOCALHOST\Instance" />
<add key="databaseName" value="database" />
</appSettings>
</configuration>