This issue may happen if Prequel doesn't have access to your files. Please make sure that you've allowed Prequel to access your photos.
To do that, please:
To do that, please:
Step 1
Go to Settings > Apps.
Step 2
Find Prequel and go to Permissions > Storage.
Step 3
Make sure that Storage is on and has access to All Photos.
* Please note that names of sections may vary depending on your device manufacturer.