Web Front End for PS script - issues with PS remoting

As I commented, I can't help you with JEA as I have no experience with that. But I have done troubleshooting with Powershell and IIS, so here are some suggestions.

In the Powershell script on the web server, generate a transcript. Try doing a simple Invoke-Command to a remote server. Verify that the account can authenticate to the remote server and do something simple like displaying environment variables.

Start-Transcript -Path C:\SomeLogFolderName\MyScript.log
Invoke-Command -ComputerName dcName  -ScriptBlock {$env:USERDOMAIN;$env:USERNAME}    
Stop-Transcript

Then try with a session as you had posted.

Start-Transcript -Path C:\SomeLogFolderName\MyScript.log
$session = New-PSSession -ComputerName dcName -ConfigurationName DomainAdmins
Invoke-Command -Session $session   -ScriptBlock {$env:USERDOMAIN;$env:USERNAME}    
Stop-Transcript

If you don't get a good error message in the transcript, then I would think that there would be an error logged somewhere. The main problem with that is the multitude of eventlogs in Windows. I put together a Powershell script that I called RecentEvents.ps1. I posted it here.

https://zcusa.951200.xyz/en-us/answers/questions/102481/eventlog-madness

It will read all of the event logs and display the entries in a gridview that is sorted by time of day. Recreate the error and make note of the current time. Run the script (using run as administrator) on both the source and destination servers. Scroll the grid to the time of the error and see if there are any events that are related to remoting or to the account you used. You may need to review and modify your auditing settings so that your servers log logon failures, and maybe object access failures.

Then there ought to be some error in an eventlog on the remote system.

Then I would expect there to be a logon failure event recorded in the Security eventlog on the 3rd server.

Can your script see the shares on the remote server?

net.exe view \\dcname

Assuming that "dcname" is an Active Directory domain controller, try accessing a member server instead. Be sure to add the AD service account (IIS worker process identity) to the Administrators group on the member server.

Maybe something here...

https://zcusa.951200.xyz/en-us/powershell/scripting/security/remoting/ps-remoting-second-hop?view=powershell-5.1

Or here.

https://zcusa.951200.xyz/en-us/powershell/scripting/security/remoting/jea/security-considerations?view=powershell-5.1

Why do they think this is a double hop issue? From you've explained, I only see 2 servers. Server1 (IIS+Powershell.exe) and Server2 (that you've named dcName). Where is the 3rd server?

As I commented earlier, what I did was to use a normal AD account that I put in the administrators group on various member servers. I then defined that user to an IIS app pool where I entered its password. It was then able to access those servers. For that site I did not use Powershell remoting. It's function was to manage local group membership so I used the ADSI interface in an .aspx page.

 oG = New DirectoryEntry("WinNT://" & strThisServer & "/" & strThisGroup & ",group")
 oG.Invoke("Add", "WinNT://" & strThisUser)

If dcName refers to a domain controller, then maybe try accessing a member server. Or try using a different account. Did you try running the "net.exe view" statement? Was it able to see any shares?