📌 : If your hardware supports it, always upgrade to the latest version. If you are using a 2015 version due to hardware limitations (like an old CPU), ensure you are at least using the last supported stable build for your architecture.
: Avast has migrated its licensing systems; most keys generated in 2015 are no longer recognized by the current activation servers. Avast-Antivirus-License-keys-2015-plus-Activation-code-Free
For legacy machines with no internet access (common for 2015 versions): 📌 : If your hardware supports it, always