Always 401 on POST buy?

Not sure if this is the correct place to ask as it relates to be trying to automate buys in my personal Coinbase account. If it needs to be moved somewhere more appropriate feel free.

Otherwise:

What's wrong with this? Why can't I POST a buy? I keep getting 401 Unauthorized. The API has the correct permission (wallet:buys:create)

I should point out, that my GETs work, I can read all information from the account.

$time = 'https://api.coinbase.com/v2/time'
$epochtime = [string]((Invoke-WebRequest $time | ConvertFrom-Json).data).epoch

$method = 'POST'
$requestpath = '/v2/accounts/xxxxxxxx-3ecb-xxxxxxxx-xxxxxxxx/buys'
$endpoint = "https://api.coinbase.com/$($requestpath)"
$secret_key = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'

$sign = $epochtime + $method + $requestpath
$hmacsha = New-Object System.Security.Cryptography.HMACSHA256
$hmacsha.key = [Text.Encoding]::UTF8.GetBytes($secret_key)
$computeSha = $hmacsha.ComputeHash([Text.Encoding]::UTF8.GetBytes($sign))

$signature = ([System.BitConverter]::ToString($computeSha) -replace "-").ToLower()

$header = @{
"CB-ACCESS-SIGN"=$signature
"CB-ACCESS-TIMESTAMP"=$epochtime
"CB-ACCESS-KEY"='xxxxxxxxxxxxxxxxxxxx'
}

$body = '{"amount": "10", "currency": "XLM", "payment_method": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx", "commit": "true", "quote":"false"}'
function Get-CoinBase($method, $endpoint, $header, $body)
{
  $result = Invoke-WebRequest $endpoint -Headers $header -Method $method -body $body -ContentType "application/json" -UseBasicParsing
  write-host $APImethod -f yellow

  return $result
}

$AccountBAL = Get-CoinBase -method "POST" -endpoint $endpoint -header $header -body $body

coinbase / coinbase-commerce-node

Always 401 on POST buy? #55