There may be an issue with your online project loading on the Chrome web browser when your Start Up sequence is a 360° video. This could be related to Google Chrome's autoplay policy:
If you would like to fix the issue only on your computer you can go to chrome://flags/#autoplay-policy and change the default setting to "No user gesture is required".
As a workaround for all users who will have access to your online project, you can create a 'Play/ Start' button that the user need to click/gaze on before jumping to the video sequence.
In general, this is already good practice in VR experiences as it gives the user an introduction to the project, can provide them with instructions and allows them to commence when they are ready.