It is not possible to create requests in Service Desk through SOAP.
SoapUI interface and jsvr.log show the following error message:
java.lang.ClassCastException: class java.lang.Integer cannot be cast to class java.lang.String (java.lang.Integer and java.lang.String are in module java.base of loader 'bootstrap')
std.log shows the following message:
Spell interp failed at cr.spl:597:cr::init_call_request: set_attr on created_via failed: NOT FOUND 3551
CA Service Management 17.1 and higher.
Somehow the table "interface" does not have all necessary entries and causes this issue when populating the field created_via in the ca_contact table.
Double-check the table "interface".
If it does not have all the necessary entries, you can have unexpected issues when creating requests.