What is your Shotcut version (see Help > About Shotcut)? Is it 32-bit? 22.03.30. How can I determine if my Shotcut is 32-bit?
Can you repeat the problem? If so, what are the steps?
Please see screenshot below. As you can see from the attached log, I could export H.264 Baseline, High, Main all perfectly. But for Lossless H.264, the resulting .mp4 featured just audio, no video! Why?
What are you using to play the video? Quite a few video players cannot handle lossless MP4 videos. If you can open the lossless video in Shotcut and play it OK then this is your problem.
Why are you creating lossless MP4 in the first place?