If Messages is indexing and shared links and photos don’t appear in your conversations
If you can’t find photos from your conversations or see an alert about Messages indexing, you might need to check your iCloud settings for Messages.
When you update your iPhone software or transfer your data to a new iPhone, you might notice a delay in your shared links, photos, or other media appearing in Messages conversations. Shared links, photos, and more will be shown once Messages finishes indexing. Data transfers require Wi-Fi connectivity and the indexing process completes more quickly when your iPhone is locked and connected to the Internet via Wi-Fi or Ethernet. Depending on what tasks are running in the background and the size of your saved Messages data, the process could happen quickly or take up to a few days to complete.
If you previously used iCloud to back up your data and can’t find shared links, photos, or other media in Messages conversations after some time, you can turn iCloud for Messages off and on to restart the indexing process:
In the Settings app, tap your name.
Tap iCloud.
Tap Messages.
Turn Use on this iPhone off and then on again.