Unlocking a password-protected Siemens S7-1200 PLC requires a factory reset using a blank SIMATIC Memory Card, which permanently erases the existing user program. The procedure involves inserting a prepared card into the CPU, cycling power, and, if necessary, using TIA Portal to restore factory settings. For detailed, official procedures, consult the Siemens SiePortal documentation. SIMATIC S7 S7-1200 Programmable controller - ID: 107623221

This is the most reliable way to unlock a PLC if you cannot access it online due to the password. Prepare a Siemens SIMATIC Memory Card

To avoid future password-related issues, keep the following tips in mind:

S7-1200 password unlock

Here’s a helpful, responsible write-up regarding for Siemens PLCs.

Part 1: Understanding the S7-1200 Security Architecture

Unlocking a password-protected Siemens SIMATIC S7-1200 PLC typically involves a factory reset