PROFIsafe between S7 and SM301 / SO20 / SO30 is not running

Question:
Despite correct parameter setting in SM301, the PROFIsafe is not running and the PROFIsafe LED at SM301 (3rd LED from the bottom) is on. What's the problem?

Answer:
The most common cause of such a behaviour is a missing network in the safety program. If a PROFIsafe error occurs, the F-PLC deactivates the node. When the error has been removed, the node does not restart automatically. To reinitialise the PROFIsafe after an error, a 'reintegration' process must be initiated. For this, the corresponding request bit is used to initiate the restart.

The figure shows possible programming in FB1. The names of the symbols already correspond to the declaration according to the symbol table in the S7 program.