It is showing 0 because what you now have is a new empty wallet (with new seed). You need to restore your old wallet from your original seed before you will be able to see the balance. When you first run Mycelium it should give you the option to either "Restore from Backup" or "Create New". You will need to uninstall Mycelium and reinstall it and try again.
Also, Mycelium on iOS has not been properly updated in over a year!!?!
If all else fails, you can probably restore your Mycelium seed into another BIP39/BIP44 compatible wallet.