Hi,
Try to following these to resolve the search problem in AquaMail:
Restart the App: Sometimes a simple restart can fix temporary glitches.
Clear Cache: Go to your device settings, find AquaMail, and clear the cache.
Update the App: Make sure you are using the latest version of AquaMail. Check for updates in the Play Store.
Re-index Emails: In AquaMail, go to Settings > Mail, receiving > Reindex email database. This can help if the search index is corrupted.
Reinstall the App: If all else fails, try uninstalling and then reinstalling AquaMail. Make sure to back up your settings and emails if needed.
Hope this helps!