I'm able to create a JSON datasource and fetch data using GET method so a I couldn't reproduce your issue.
I'd suggest you to take a look the documentation about the ["Path types in Virtual DataPort - HTTP"](https://community.denodo.com/docs/html/browse/6.0/vdp/administration/creating_views/importing_data_sources_and_creating_base_views/path_types_in_virtual_dataport#http) and the ["Execution Context of a Query and Interpolation Strings"](https://community.denodo.com/docs/html/browse/6.0/vdp/vql/advanced_characteristics/execution_context_of_a_query_and_interpolation_strings/execution_context_of_a_query_and_interpolation_strings) to check if everything is configured properly.
Take into account that dates usually causes issues in terms of format so require special attention when configuring these fields. Maybe you could enable the logs on your website to check that the request sent by Virtual DataPort is correct.
Also, you could take a look to the [JSON](https://community.denodo.com/docs/html/browse/6.0/vdp/administration/creating_views/importing_data_sources_and_creating_base_views/json_sources) and [Delimited files](https://community.denodo.com/docs/html/browse/6.0/vdp/administration/creating_views/importing_data_sources_and_creating_base_views/delimited_file_sources) sources configuration.
Hope this helps!