Hey Roelof, I’m guessing you have “auto play videos” turned on A lot of folks, don’t realize that if you have “auto play” turned on in SETTINGS/PHOTOS it will automatically mute your videos, requiring u to manually turn sound on for each video. it’s actually a smart feature because auto play can be very loud in situations where you might not want everyone in a meeting hearing uncle Bubba cursing. Also, in situation’s during performances or kids recitals if you take a short video and want to make sure it’s good you don’t want it blasting through the auditorium just from checking it
-So first check out your settings for the Photos app
-Also: Be sure ‘do not disturb’ is off as that silences several things by default on iPhone/iPad, requiring you to turn the videos sound on manually, even when you have auto play, turned off in settings.
I hope this helps…