DBCC on SSAS Cube fails DBCC on the Cube fails(SQL version 2014 SP2, 12.0.5000.0).
My XMLA query:


Error message:
Executing the query ...
The DBCC element at line 7, column 88 (namespace https://schemas.microsoft.com/analysisservices/2016/engine) cannot appear under Envelope/Body/Execute/Command.
Run complete

I can find anything wrong with a query.Tried 2003 and 2014. According to books online, it should just work:
https://docs.microsoft.com/en-us/sql/analysis-services/instances/database-consistency-checker-dbcc-for-analysis-services?view=sql-server-2017
Did you read the rest of the docs?


  Output when running DBCC against an earlier version of Analysis
  Services
  
  DBCC is only supported on databases running on a SQL Server 2017
  instance. Running the command on older systems will return this error.


Executing the query ...  
The DBCC element at line 7, column 87 (namespace http://schemas.microsoft.com/analysisservices/2003/engine) cannot appear under Envelope/Body/Execute/Command.  
Execution complete


Updated
Here is a link that explains things a bit more in detail than the docs you're are referencing.

https://www.mssqltips.com/sqlservertip/4077/consistency-checks-for-sql-server-analysis-services/