I have tried this and it worked in my tests. See if it works on your end.
When providing the Url for the Custom webservice, you might be doing some
Instead change that to include the Organization Name
Note: Org Name is not the Fridnly name but the Unique name, so it should not
have any spaces. If your friendly name i same as unique name then you can
get it in Context.OrganizationName property else, you have to get it in
using configuration attribute on the SdkMessageProcessingStep.
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