A blank export usually happens when your phone doesn't have enough memory to complete the export. Certain GPUs and firmware can sometimes cause issues as well.
If you're getting black images upon export, first try completely closing the app and opening it again.
Next, try restarting your device, which should free up more memory.
Finally, try editing a smaller resolution image. Images captured on your device work best. Large images captured on DSLR cameras can sometimes have too high of a resolution for mobile devices to handle complex image processes on. You can always try reducing the resolution of your images or converting them to jpegs before editing.
If the problem persists, feel free to submit a help request and be sure to provide the following information:
- Your device model
- App version
- Source of the image (phone, type of camera, etc)
- Attach an example of an image you're trying to edit
- What effects are you using in the export?