Powershell New-ADUser Password Complexity Exception - powershell

Question

I'm trying to mass import AD users from a CSV file. But I keep getting the following error:
The password does not meet the length, complexity, or history requirement of the domain
But the password that's created with $InitialPassword has uppercase, lowercase, numbers and special characters so I don't get what it's not meeting.
ForEach($user in $CSV){
$FirstName = $user.Voornaam
$LastName = $user.Familienaam
$DayOfBirth = $user.geboortedatum
$Enrollment = $user.inschrijvingsjaar
$Classroom = $user.Klas
$PhoneNumber = $user.contactnummer
# create and sanatize username
$UserName = "$($FirstName.ToLower()).$($LastName.ToLower())"
$Username = $UserName.Replace(" ", "")
# generate password
$InitialPassword = (ConvertTo-SecureString "$($FirstName[0])$($LastName.ToLower())$($Enrollment)!" -AsPlainText -Force)
New-ADUser -Name "$FirstName $LastName" `
-GivenName "$FirstName" `
-Surname "$LastName" `
-UserPrincipalName ("{0}#{1}" -f $UserName, "arrow.local") `
-SamAccountName $UserName `
-Initials "$($FirstName[0])$($LastName[0])" `
-DisplayName "$FirstName $LastName" `
-HomePhone $PhoneNumber `
-Description $Classroom `
-Office $Enrollment `
-AccountPassword $InitialPassword `
-Enabled $true
Write-Host "$UserName"
Write-Host "$InitialPassword"
}

Answer 1

The default password complexity rules disallow the account's name or username in the password - so when you compose the password of strings that also go into the Display Name, you're in violation of the complexity requirement!
If you're also seeing errors due to invalid user names, be aware that sAMAccountName attributes must be:
Unique at the forest-level
No more than 20 characters long