Error Unable to Clear Cache (iOS)

Hello @Лариса21788468ldth 

I cannot reproduce any trouble using either a free or paid account... Have you tried restarting your device?

Using a free account that does not sync to Lightroom cloud storage, there is no Clear Cache function.  I added hundreds of photos, and then deleted the photos (and also emptied the trash inside the Lightroom app), and in iOS Settings > General > iPhone Storage > Lightroom, I see Documents & Data goes back to the original low amount used.

Using a paid account, I similarly imported and then synced photos, and after photos finished syncing I was able to see and use the 'Clear Cache' funtion Lightroom Settings > Local Storage.

Can you write clear steps or share a video screen capture showing what actions you are trying, and what the issue looks like?

Also, please try doing a full Backup and Restore of your device (using iCloud or iTunes/Finder).  I wonder if the Restore process might smooth out some corruption.