Need help for lazyloading

Hi all,

i have a table of 50.000 rows
i made a standard load service for a grid on this table
it worked fine returning 50.000 rows
I have dhtmlxSuite Pro 8.3.9

I adapt my service for lazyload
so with
var lazyDataProxy = new dhx.LazyDataProxy(url_dila_rar_liste_lazy, {
limit: 5000, //i expect that this will throw 10 requests of 5000 each
prepare: 5, //note that i don’t understand for what this is useful
delay: 150, //i expect that each request will be launched every 150ms
from: 0 //i expect that first request will be launched with this parameter
//will be launched first with 0, second with 5000, third with 10.000 and so on
});

the output is :
{
data :[…], // data retrieved from my table with rank between from and from+limit
total_count: 50000, // total_size of the table
from : 0 //identical to from parameter
]

when i launch it, the get url launched is
https://apex.qualif.pgi.dila.fr/ords/apex_ebs_extension/dila_rar/liste/lazy/0/18810/1?limit=5000&prepare=5&delay=150&from=0&responseType=text

I receive correctly in my grid the first 5000 rows,
but no other requests are launched in background to receive the other 45000 rows

do you have any idea what is wrong ?