<METHOD DOES NOT EXIST> Error getting when call method from ClassMethod.

calling Method from ClassMethod

This is the problem. A Method needs to be called in the context of an instantiated object. A ClassMethod by definition isn't associated with an instantiated object.

If it's necessary to do it this way, your ClassMethod could use %New() to instantiate an object and then call the Method on that object:

set myObj = ##class(My.Object.Class).%New()
set tSC=myObj.myMethod()

But, it looks like you're working with a Business Service class. For that, it isn't enough to simply use %New(). You need to use Ens.Director::CreateBusinessService to instantiate the object before calling the Method.

https://docs.intersystems.com/irisforhealth20212/csp/docbook/DocBook.UI....

SendRequestSync   is an object method that requires an object as the base.
##class(Ens.BusinessService).SendRequestSync(   works for ClassMethods only.
You need an object instance of Ens.BusinessService to call it.
##class(Ens.BusinessService).%New().SendRequestSync( 
might be a dirty workaround