Ok that version now officially supports the newest AI - SenseAI, so maybe something wonky with your setup and using Deepstack. Some have reported issues.
I had a similar issue and solved it by reinstalling Deepstack. You have to make sure that you uninstall Deepstack and then delete the Deepstack folder as well.
Steps
1. Download new Deepstack from the Deepstack website
2. Go into Blue Iris and turn off Deepstack in Settings/AI
3. Go to the start menu and the Deepstack folder and click the uninstall link
4. Go to the File Explorer and navigate to the directory were Deepstack is installed (probably C:\Deepstack) and throw the entire directory into the trash
5. Run the install exe that you downloaded from the website in step 1
6. Restart Deepstack in Blue Iris