UPS Shipping plugin error - The request was aborted: Could not create SSL/TLS secure channel. NCver3.7

I had a client also running 3.80 who just reported the same problem, and he needed to ... Update Windows Server Cipher Suite ...

These are the Cyphers the UPS API now support and had to add as top priority in the cyphers suite.

TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,
TLS_DHE_RSA_WITH_AES_128_GCM_SHA256,
TLS_DHE_RSA_WITH_AES_256_GCM_SHA384

...using this guide to update the cyphers and everything started working again.

https://www.howtogeek.com/221080/how-to-update-your-windows-server-cipher-suite-for-better-security/

Thank you! This was the answer.
I also disabled TLS 1.1

Hello, does anyone know how to set up NopCommerce to use a proxy? That is one way we decided to get past these UPS issues. It works fine on Nop sites 4.3 and lower. But I'm having hard time finding official documentation for .net 5. We are trying to use a proxy address on a nop 4.40.4 site and not having luck.

Thanks
Cameron

I was provided the following list of cipher codes by UPS technical support:

UPS Email:
With rapid changes to security requirements, we will be eliminating several weak ciphers, and will only support the following ciphers:
o   ECDHE-RSA-AES256-GCM-SHA384
o   ECDHE-RSA-AES128-GCM-SHA256
o   DHE-RSA-AES256-GCM-SHA384
o   DHE-RSA-AES128-GCM-SHA256
To comply with our security policy, your system must have at least one of the following ciphers. However, we do suggest adding all of these ciphers to avoid potential problems