Trevor,

Most common reasons are:

1. Blank space pasted at the start/end of the code.
2. FlashScan device used to generate the unlink code was different to the FlashScan device used to generate the link code.
3. When the Tuner inputs the AutoCal V3 serial number they made a typo.

You can check #1, but 2 and 3 are items your tuner needs to check. If you need to go that path, you should provide them with your serial number and license number so it's easy for them to check/correct. Follow these instructions to the first screen shot so you can copy/paste the info to eliminate typos https://service.efilive.com/kb/artic...licenses-slots

You'll also find some information here on linking/unlinking here https://service.efilive.com/kb/artic...ocal-v3-unlink.

Cheers
Cindy