In general, the error** “error computing capabilities: Function is not executable” ** occurs when there are some minor issues related to the code syntax of the Custom Function.
In order to resolve this error, I would perform the following checks in the code for the Custom Function:
* Check whether the code syntax is correct.
* Check if all the annotations are provided according to the correct format.
You can take a look at the[ Creating Custom Functions with Annotations](https://community.denodo.com/docs/html/browse/8.0/en//vdp/developer/developing_extensions/developing_custom_functions/creating_custom_functions_with_annotations) section of the Virtual DataPort Developer Guide for more information on the correct syntax to use when developing a Custom Function.
Hope this helps!