Can't get the "basic java executor" example to work

I'm trying the sample at https://github.com/neo4j-apps/graph-app-starter/tree/master/examples/basic-java-executor
Followed the instructions in readme and was able to build and install the app successfully. But just can't get it to run.

Running it off localhost and clicking "Execute Main class" returns

"Error: Could not find or load main class Main"

Clicking "Execute jar" does nothing

Running it off the file system directly and clicking either button gives,

"Could not read app permissions. Graph app not found for internal id 'DESKTOP_DEVELOPMENT_APP'

(On Neo4j desktop version 1.2.1)

How can I get it to work ?

Thanks