This is on both IOS and Android versions. I know it was 'fixed' in 2017 but has reccured.
Started in the latest version (1.14.0 / 1.14.1), mob spawners no longer have the mob spinning around inside spawner. Was there in earlier versions but has suddenly gone in one of the updates. I do not have any texture packs on that effect spawners. The spawner still spawners mobs but the spawner cannot be identified without it spawning mobs or in peaceful mode.
Thank you for your report!
However, this issue is a Duplicate of MCPE-56879.
If you would like to add a vote and any extra information to the main ticket it would be appreciated.
If you haven't already, you might like to make use of the search feature to see if the issue has already been mentioned.
Quick Links:
📓 Issue Guidelines – 💬 Community Support – 📧 Customer Support – 📖 Game Wiki