I faced this issue before but I did not use certificates so kindly add activity called (Invoke code) and add this code in it
Function(se As Object,
cert As System.Security.Cryptography.X509Certificates.X509Certificate,
chain As System.Security.Cryptography.X509Certificates.X509Chain,
sslerror As System.Net.Security.SslPolicyErrors) True
and put this acitivty direct before HTTP Request please try it and feed me back if you still face the same issue
from attached screen there is no body in your request also make sure from body format if it text/xml or application/xml according to your API also you marked enable SSL certificate verification. My recommendation print your request before HTTP request activity and try it on soup or reset according to your API.
Please hide your end point if it critical data.