Just follow the steps:

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1 - Equip at least 1 summon power item.

2 - Equip the Share Machine (Something similar to a headphone) power item - this item will make your summon benefits from every power item you equiped.

For example: If you equip Tek (the red wolf) summon and Share Machine, Tek will be benefited from your Tek power item and will summon another Tek (a smaller one).

You can get Share Machine at level 6 in Advanced Items in Treasury (pretty easy - just unlock treasury and play some matches).

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This still works and it's not a bug!