I bought full blue iris from this site a few years back. I built a new PC and just set it upand applied my license key but i get BLUE IRIS EVALUATION VERSION watermarks. Does the license only work for a certain time it did not state it was an annual key.
You still have access to use the version you purchased and that version did not expire.
Since you didn't get the watermark until you built a new computer and applied the latest version, you were operating just fine with an older version because if you had updated you would have got the watermark.
Based on your dates, you have access from version 5.4.9.18 to 5.6.0.10
You can find any of those versions from 9/10/21 to 9/10/22 here:
Simply download one of those and your evaluation watermark goes away.
It clearly states on the website about the maintenance if you chose to purchase. As I said, you were operating fine before on an older version and many of us here find a version that is stable for us and stay on that version until BI adds a feature we want or need.