If you don't have docker installed before your first run, hardhat-scilla-plugin will refuse to deploy the first contract in the contracts/ directory

[rrw-zilliqa]

... because you don't have docker installed, so the command to analyse the first contract will fail, producing invalid output that will then be cached. This will cause the plugin to create an invalid deployment request and you will get an INVALID_JSON error when trying to execute the request.