The log likely has some information - you might have to dig through to find it. You may also want to look at sys.dm_hadr_database_replica_states and see what's in there. For example, what does the following tell you about the state, any reason for suspended?
SELECT
DB_NAME(database_id) AS DBName,
synchronization_state_desc,
synchronization_health_desc,
database_state,
database_state_desc,
suspend_reason,
suspend_reason_desc,
last_sent_time,
last_hardened_time,
last_commit_time
FROM sys.dm_hadr_database_replica_states
WHERE is_local=1
Sue