OK, I downloaded the latest and did a re-install; it noticed some old bits and brought me back to current as far as I can tell.
Still have the problem. When I go to export as AVI (using Chrome browser, works same in other browsers), it initially offers to do a short clip of a few seconds (<20secs). If I click on the arrows it might change to zero seconds:
View attachment 30657
and clicking a few more times might make it have a negative size:
View attachment 30658
OK, it's probably something silly I'm doing. What am I doing wrong?
That is because you have some early version in use. Are you sure you downloaded the latest version or is it extracted to right location? I suggest that you delete all folders and files from Program Files/Blue Iris 4/www and extract the latest ui3-34.zip in that www folder.
https://github.com/bp2008/ui3/releases/download/34/UI3-34.zip