Issue with adding the user to the DL (AD user creation + Add user to SG's + Create office 365 mailbox + Add user to DL)

I have created a script that would perform - AD user creation + Add user to SG's + Create office 365 mailbox + Add user to DL

Here is the script below - 

#############################################################################################

Import-Module ActiveDirectory -ErrorAction Stop

Import-Module MSOnline

Connect-MsolService

$adusers = Import-csv 'C:\Program Files (x86)\scripts\ADUsers.csv'

#This will process the CSV row by row. Each row contains information to create an active directory account for a user. 

foreach ($user in $adusers) 

{

   $username = $user.username  

   $password = $user.password

   $firstname = $user.firstname

   $lastname = $user.lastname

   $surname = $user.surname

   $GroupName = $user.GroupName

   <#write-host "username :"$username

   write-host "password :"$password

   write-host "firstname :"$firstname

   write-host "lastname :"$lastname

   write-host "surname  :"$surname

   write-host "GroupName :"$GroupName#>

#create AD Acct sets for username  #sets account name      #sets first name   #sets lastname  #enables account #sets display name        #sets login script path

New-ADUser -samaccountname $username -name "$firstname $surname" -givenname $firstname -surname $lastname -enabled $true -displayname "$firstname $surname"  -accountpassword (convertto-securestring $password -asplaintext -force)

if (Get-ADUser -Filter "surname -eq '$lastname' -and givenname -eq '$firstname'")

{

write-host "User Found"

}

else 

{

write-host "Did not Found user"

}

#Adding Users to Security Groups

Add-ADGroupMember  -Identity "security group 1" $username 

Add-ADGroupMember  -Identity "security group 2" $username

#Adding Users to DL

#Add-ADGroupMember "Distributionlist@domain.com" -Members (get-aduser $username)

#Moving users to OU

Get-ADUser $username | Move-ADObject -TargetPath 'ou=company,ou=Accounts,DC=TEST,DC=local'

###############################Creating office365 Accounts###########################################

#Below will rise popup,Credentials will store to the variable $LiveCred after entering credentials

$Office365Users = New-MsolUser -DisplayName "$firstname $surname" -FirstName $firstname -LastName $lastname -UserPrincipalName $firstname@domain.com –PassWord $password

}

##############################################################################################################

Every thing is working fine and the only issue i have got here is the user is not getting added to the DL (The DL already exists)

#Adding Users to DL
#Add-ADGroupMember "Distributionlist@domain.com" -Members (get-aduser $username)

I am not sure what i am missing here - have been trying to lot to resolve this issue ! Can you help further ?