Was this setup previously working? Did you make any changes to either the camera or Web Presenter?
If it suddenly stooped working, double check that the cabling is still good.
What resolution/framerate are you currently outputting from the camera? 1080p29.97 usually works well with Blackmagic gear when using the SDI output from our cameras. That would be dial position C on the back of the camera. Did you test the HDMI by going into the Blackmagic device or a separate HDMI display? If possible it would be useful to check the HDMI signal by connecting it to a display with a known working cable and see if you are getting a video feed there. You may need to adjust the output resolution of your camera depending on what resolution the display supports.
If you are still having trouble you can reach out here or try contacting support. The number for support is 484-593-2584 or you can submit a ticket here, https://help.ptzoptics.com/support/home