HSP0276 is specifically for TIA Portal V15.1 ; firmware V4.3 is natively supported in V16 and newer. Installation Steps

If your physical PLC is running an older version (e.g., V4.2), download the S7-1200 CPU Firmware update V4.3 (Entry ID: 109764327) to flash the device itself. Step 2: Install HSP0276 in TIA Portal

FACT: S7-1200 FW4.3 only for Step7 V15.1 - Siemens SiePortal

Allows you to load and manage certificates created in STEP 7 directly on the CPU.