Error during _msearch call processing, cause: Empty request body for _msearch

Hi,

I have created a connection to our elastic search database, it seems ok but I can’t get any data, all my requests resulting in the following error (Query Inspector) :

xhrStatus:“complete”
request:Object
method:“POST”
url:“api/datasources/proxy/30/_msearch”
data:"{“search_type”:“query_then_fetch”,“ignore_unavailable”:true,“index”:[HIDDEN],“max_concurrent_shard_requests”:256} {“size”:0,“query”:{“bool”:{“filter”:[{“range”:{"@timestamp":{“gte”:“1550074283599”,“lte”:“1550247083599”,“format”:“epoch_millis”}}},{“query_string”:{“analyze_wildcard”:true,“query”:":"}}]}},“aggs”:{“2”:{“date_histogram”:{“interval”:“2m”,“field”:"@timestamp",“min_doc_count”:0,“extended_bounds”:{“min”:“1550074283599”,“max”:“1550247083599”},“format”:“epoch_millis”},“aggs”:{}}}} "

response:Object
error:“Error during _msearch call processing, cause: Empty request body for _msearch”
errorId:“2469147086596”
status:“400”
message:“Error during _msearch call processing, cause: Empty request body for _msearch”

I have no clue of what I am doing wrong.

Regards
Frédéric