I have recorded a 35 minute movie. I have added music to it, and just before the movie is supposed to play, my music disappears! It says the music should play, but it doesn't!
You may want to check your iPhone has enough memory / storage space free for your projject.
Eg: An iPhone generally needs around 8 Gb free in which to operate smoothly.
How to check the storage on your iPhone and iPad - Apple Support
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If you haven't seen it already:
Apple support's article below may help trouble-shoot.
Add music and soundtracks in iMovie on iPhone - Apple Support
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NB: Above article also says:
Note: To use a song you purchased from the iTunes Store in your project, you must be the copyright holder of the song or have express permission from the copyright holder.
For more information, see the iMovie for iOS and iPadOS software license agreement.
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Useful resource: iMovie User Guide for iPhone - Apple Support
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iMovie Support website:
More info: Support: Contact options etc:
iMovie - Official Apple Support