There's two things to try:

Clearing the Techtree

This can help many data related errors and issues occur with it when we have updated the game without needing a version update from appstore, meaning you won't see "Update" for the app. But you will need to update the techtree for the new data to show up in your account.

Clear the Cache

This can help resolve visual errors related to images or assets that are not loading. It is similar to reinstalling the app and downloading it again from the appstore.  When you do this it typically means you will need to re-download the majority of the games in-game assets, which may mean when you reinstall the app it will take a bit longer to load.

To Clear Techtree:

1. Tap on the arrow in the lower left corner of your game screen.

2. Tap on the + icon labeled "Extras".
   

3. Tap  Clear Tech Tree

4. Restart the app and check if the issue remains.
5. If you are still having issues, please submit a Help Ticket!

To Clear Cache:

1. Tap on the arrow in the lower left corner of your game screen.

2. Tap on the + icon labeled "Extras".
   

3. Tap Clear Cache.

4. Restart the app and check if the issue remains.
   
   
5. If you are still having issues, please submit a Help Ticket!

These troubleshooting step can help in many cases and will not mess with your account progress in anyway. If any issue or bug still persists after trying these steps, please open a help ticket for us investigate and assist further!