Use custom connector in Power BI Services ?

I'm pretty new in the creation of a custom connector but I was able to build something which works in power bi desktop
Now, I would like to make some refresh online, so I follow the following tuto:
Custom Data Connector: How to Deploy and Test - Microsoft Fabric Community

And the test connection has been implemented and it is successfull

my .mez files is well deployed on my server 

In Power BI Services, I go in manage gateway, there I'm able to select the gateway that I deployed on my server; but when I try to create the connection, it is returning the following error message:

Unable to create connection for the following reason:
Unable to connect the data source. Either the data source is inaccessible, a connection time out occured or the data source credentials are invalid. Please verify the data source configuration and contact a data source administrator to troubleshoot this issue.

Details:

Test-GateWay: We cannot convert the value null to type Logical.

The only settings required by my connection is the api url, everything is working perfectly in Power BI desktop but not in services.

I installed Power BI desktop on the server on which the gateway is installed, and I am able to use the custom connector in Power BI Services, so the server is able to query the API

Any idea of how could I try to debug that?

Many thanks in advance for your help