Dear Johan Kooistra,
Thank you for reaching out with your concern.
After discussing the matter with one of our developers, I’d like to clarify that, for some security reasons, video files uploaded via (FTP or Joomla media) are not accessible in the SP Page Builder media manager. To use your video, it must be uploaded directly through the SP Page Builder media manager.
Solution:
I noticed that your server currently allows uploads of up to 8MB. To resolve this, you will need to adjust the following settings in your php.ini file via your hosting settings:
upload_max_filesize = 20M
post_max_size = 20M
For reference, you can check this screenshot: https://prnt.sc/4r2Yp9FdMkYw.
Hopefully, this will resolve the issue. Please let me know if you need further assistance!
Best regards