I have the same issue described in https://community.adobe.com/t5/lightroom-ecosystem-cloud-based-discussions/lightroom-cc-for-mobile-e...
When trying to export a set of images from LR on my mobile, I didn't get a single image exported. Instead, I got the error message "export failed".
I am using Lightroom Android 8.4.2 on Huawei P30 Pro / Android 10.
Clearing the app cache does not resolve the issue.
I can see the sync icon rotating in the background what made me think: how does export work? Will raw images be downloaded and converted locally? Or is a jpg genersted in the cloud and then the exported file is being downloaded?
I switched from a bad wifi connection to my slightly better mobile network: export works for the first couple of pictures, but very slow, and then fails. Hence, my assumption is that LR first downloads huge raw image to then locally convert (what does not make sense to me if there is the power of a cloud service available in the background compared to a slow mobile and a potentially slow network).
Trying the same in my (high speed) home wifi resolves the issue.
Conclusion: export feature is not designed for slow connections and may need rework to better support mobile users.
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