Hello there.
Solution to Bitdefender 2016 subscription expired though having valid subscription:

Use different Email ID for my.bitdefender.com & central.bitdefender.com
Initially you have to keep same Email ID to migrate from My to Central, once you migrated change Email ID of either one and use Central's detail for the product's activation. Once done follow steps:
1. Uninstall(for safe), clean registry and reboot.
2. Remove any previous device from My and Central accounts, make sure same or unused device is not listed.
3. Reinstall using link in your Central account, it will automatically active on successful install.
4. Use Central's detail to activate if used trial version initially.

Hope this helps.
Regards.
AD

