[API_V3] Trouble with session start.

Hello everybody.

I installed KalturaCE and the admin works fine. I'm very crazy about this product since I installed it. It's incredible wath we can do with it as so simply.

But, if I try to test api_v3 I call http://mydomain/kaltura/api_v3/web/sample/media_gallery.php and the script return :

"
An error occured while trying to list media entries.
Error message:

Action "start" does not exists for service "session"

"

I looked for the code and the value (PARTENER_ID, SECRET, ADMIN_SECRET, SERVER_URL) in web/sample/config.php seems to be good.

In logs I obtain this :

1243239855.51 1592054989 INFO: >------------------------------------- api_v3 -------------------------------------
1243239855.51 1592054989 NOTICE: API-start [session][start][1]
1243239855.51 1592054989 ERR: exception 'KalturaAPIException' with message 'Action "start" does not exists for service "session"' in /home/elgg/video/kalturaCE/kaltura/api_v3/lib/KalturaDispatcher.php:53
Stack trace:
#0 /home/elgg/video/kalturaCE/kaltura/api_v3/web/index.php(34): KalturaDispatcher->dispatch('session', 'start', Array)
#1 /home/elgg/video/kalturaCE/kaltura/api_v3/web/index.php(139): IndexContext->IndexContext()
#2 {main}
1243239855.51 1592054989 NOTICE: API-end [session][start][1] [0.0011899471283]
1243239855.51 1592054989 INFO: <------------------------------------- api_v3 -------------------------------------

Can you tell me how to resolve it, or where I can found the answer ?

Thank's for your help !
Christophe