Powershell cmdlet to install a CA certificate on c7000 Onboard Administrator

I have 200 c7000 enclosures and need to get valid SSL certificates installed on them via Powershell.  Generating the .csr file is working fine via Powershell.

But when I try to use the Add-HPOACertificate command (from the HPOAcmdlets module) to install the .cer file, I get an error.  My .cer file is legit - I can browse to the OA GUI and paste the file contents in - the OA resets and then I can see my new certificate.   But when I try scripting the install using the Add-HPOACertificate command, it quickly returns the error "The CA certificate is invalid." 

Here are the 2 key lines in the Powershell script:

$Target_Cert = Get-Content $Certificate_File -Raw

$Result = Add-HPOACertificate -Connection $Target_OA -Type CA -Certificate $Target_Cert

When I display the contents of $Target_Cert it looks good, and piping it thru Get-Member confirms the data type is String.