WARN: Position forwarding failed: 0 pending

I'm trying to use the forward feature, but I'm always getting the following message:

WARN: Position forwarding failed: 0 pending

My configuration in traccar.xml

<entry key='forward.enable'>true</entry>
<entry key='forward.url'>http://my-site/send.php?uniqueId={uniqueId}&amp;deviceId={deviceId}&amp;gprmc={gprmc}&amp;protocol={protocol}&amp;deviceTime={deviceTime}&amp;fixTime={fixTime}&amp;valid={valid}&amp;latitude={latitude}&amp;longitude={longitude}&amp;altitude={altitude}&amp;speed={speed}&amp;course={course}&amp;statusCode={statusCode}&amp;attributes={attributes}</entry>

If anyone can help me, I'm grateful.

It probably means that there was an error.

Juliano, I am using the same, works fine. Just guessing, some errors in data structure or destination server app.

ok I'll check, thank you

If your URL is HTTPS, try using different Java version. There is a known issue.

@Juliano, Where you able to solve your issue of

Position forwarding failed: 279 pending - Connection refused: connect - ConnectException (...)

I am also experiencing the same errors thus loosing some data points or in some worst cases not getting data at all.
How did you resolve yours.
Here is my traccar.xml configuration

<entry key='forward.enable'>true</entry>
<entry key='forward.json'>true</entry>
<entry key='forward.retry.enable'>true</entry>
<entry key='forward.url'>http://localhost/server/http/listener_tcp.php?uniqueId={uniqueId}&amp;deviceId={deviceId}&amp;gprmc={gprmc}&amp;protocol={protocol}&amp;deviceTime={deviceTime}&amp;fixTime={fixTime}&amp;valid={valid}&amp;latitude={latitude}

I run a WAMP version 3.2.3 for live production environment