Hey there Tututino,
Thanks for reaching out to Apple Support Communities. We're happy to provide some assistance.
Let's make sure your device and all devices involved are up-to-date. If it is updated, let's restart your device. Restarting your device and making sure it is updated can resolve many unexpected issues.
Take a look here on how to restart your iPhone: Restart your iPhone
Take a look here on how you can update your iPhone: Update your iPhone, iPad, or iPod touch
Once done, let's make sure all actions in this article were followed to ensure shared albums were set up correctly:
How to share albums in Photos on your iPhone, iPad, and Mac - Apple Support
If the issue persists, reach out to Apple directly to investigate:
Get Support
Have a great day!