My availability group doesn't work correctly I recently created an "availability group" on sql server, I created my Listener, all is well the high availability group appears well in the roles of my cluster. However I encounter a small problem, the two replicas are not really synchronized 

, then when I open my dashboard I have the error message /i.stack.imgur.com/Gf9wK.png . why it does not work ? I have already done everything but nothing done.

I use windows server 2012 R2 and SQL SERVER 2016 Enterprise.
Can you confirm you have the correct permissions on the endpoint?

USE master;
GO
SELECT SUSER_NAME(principal_id) AS endpoint_owner
    ,NAME AS endpoint_name
FROM sys.database_mirroring_endpoints;
GO

-- change the endpoint owner
USE master;
GO
ALTER AUTHORIZATION ON ENDPOINT::Hadr_endpoint TO sa;
GO

-- grant connect
GRANT CONNECT
    ON ENDPOINT::Hadr_endpoint
    TO [yourdomain\username]; -- account used for the SQL Service