All right guys It was TLS 1.2. Though it was installed using IISCrypto the proper registry keys were not created. I located the proper registry keys from learn.microsoft.com and create the proper reg file. I also had to create a registry change to .Net framework. Now my Add-ins screen looks like Lou's picture plus the add-in was originally trying to install. Thanks for the direction.
Willie
Exchange 2016 On-Prem Organization Add-in Error

I'm trying to add an Add-in to my Organization but I get an error message as soon as I click on Add-ins. I have the needed permissions to do this however I get:
Error: The request failed. The underlying connection was closed: An unexpected error occurred on a send.
I looked this up in Technet and Google but I found no answers. Any assistance is appreciated.
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Bigwil4555 101 Reputation points
2021-09-18T04:30:44.397+00:00
4 additional answers
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Bigwil4555 101 Reputation points
2021-09-07T18:51:26.08+00:00 Lou, yes Exchange comes up as you have shown and there are no apps listed.
I attempted to run the install using this EMS command: New-App -OrganizationApp -FileData (Byte[]) and I received the same error message at the command line with a lot more stuff.
I really thought that would work.
I'll try resetting IIS later tonight as it's my understanding on Server 2019 resetting IIS causes a reboot now.
Thanks -
Andy David - MVP 121K Reputation points MVP
2021-09-02T19:19:25.863+00:00 You need to enable TLS 1.2 and disable TLS 1.0 and 1.1
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Zhengqi Lou-MSFT 8,821 Reputation points Microsoft Employee
2021-09-03T07:30:22.837+00:00 Hi @Bigwil4555 ,
See if this document helps: https://learn.microsoft.com/en-us/exchange/troubleshoot/administration/unable-install-add-ins-microsoft-store
Check TLS 1.2 status with this cmdlet: Invoke-WebRequest https://appsource.microsoft.com
Best regards,
Lou
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Bigwil4555 101 Reputation points
2021-09-15T19:23:03.687+00:00 Lou\AndyDavid, I too believe this is related to my TLS settings. Even though I have TLS 1.2 enabled the registry keys aren't matching what Microsoft says they should. I'll be making the change tomorrow night and will keep you posted.
Appreciate the assist,
Willie