wp_schedule_single_event does not call my action

Because you’re scheduling the event – even though it’s set to run immediately (i.e. with time()), it won’t fire until a second request.

So that log output is entirely expected. Try running it again, removing the code, then run once more – you should get:

[time] test_action

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)