Why might Yii::app()->user->getFlash() messages not be displayed?

Question

Yii

The site suddenly stopped displaying messages via Yii::app()->user->getFlash('message');
Although everything worked fine, no changes were made.
I also noticed that the standard captcha in Yii stopped working, i.e. you enter the correct code - but when submitting the form, the validator says that the entered code is incorrect. I so understood, any problem with sessions appeared? What could happen? I don't know which way to dig.

Answer 1

That's right, the problem with sessions, problems in setting up the server