expo-mail-composer is working properly on my emulator as well as on my actual device, but not on the client's - react-native

Question

This is quite possibly user error, although I cannot really discern how that would be the case here. I have a react native app that has the feature to record and then email videos. It works pretty simply, you press the button to enter the in-app camera, press record to record and stop to stop. Once stopped, the video is saved to the phone, and then two buttons appear; 'cancel' and 'send video'
When send video is pressed, a email composer pops up with some pre-filled information, and you can compose and send an email off of your phone just like you normally would. This works all as expected on my end, but when a client presses the 'send video' button, nothing happens. No error, no email pop up, just nothing.
I've confirmed that she signed up with her email, I've investigated the database and that's true-- so I don't quite understand what could be missing. I tried an emulator for her exact device type and it worked well, so this has to be user error or something with permissions, right?
This is the function that gets run when 'send video' is clicked...
// Sends the Video, triggers the message, opens the modal
function handleSendVid(){
saveVidToLib()
.then(resolved => {
emailVid(resolved)
})
.then(() => {
if (user.role === "GUARDIAN"){
handleSendMessage()
}
})
}
With emailVid() looking like this...
// Emails the now saved video
async function emailVid(video){
MailComposer.composeAsync({
recipients: [therapist.email],
subject: `Video Of Exercise From: ${user.firstName} ${user.lastName}`,
body: "Beta Testing",
attachments: [videoPath]
})
.catch((err) => console.log(err))
.then(() => {
setEmailSent(true)
})
}