ups setting error "UPS Service is currently unavailable, Unable to connect to the remote server"

i set up ups access key, user name and password also requested production access.
But when i estimate shipping charge and it always response
"UPS Service is currently unavailable, try again later. Unable to connect to the remote server"

i am using Nopcommerce 3.9 and Nop-Template Tiffany.

Anyone knows what i miss?

Thanks in advance!

jerry

Unless you are just unlucky enough to be setting it up just when UPS API happens to be down (which I doubt), ....

Try: Call or email UPS support and tell them to switch your account to a live account (production).

Also, check your server's network / firewalls, etc.  It's possible something is blocking your outbound https request.

thank you very much for the suggestion!
UPS switches to live account already (i have checked it).
i use my own windows reseller hosting. i have another site encounters same problem with USPS setting.
i guess it's my Plesk windows service plan configuration causes this problem.
still looking for the solution.