no bonus

Same here. Upgraded sponsor card states the value is X+1, meaning if it is in your 5th slot you can play a 6 power sponsor card. In the current version the game does not allow you to play the 6 power card.

I know what he is talking about. The bonus is the +1 that you get to sponser strength when it is upgraded. To be clear, when you upgrade the Sponsor card, the strength of the card changes from X to X+1.

This bonus is correctly added for cards that cost 5 or less. This means your upgraded sponsor card can be in position 3, and the game allows you to pay for a sponsor card with a cost of 4. In this example X = 3, so X+1 =4. Working as intended.

However, when your upgraded sponsor card is in position 5, as just happened in this game, the current build does not allow you to play a cost 6 card as it should. X = 5, so X+1=6, but a 6 cost card will not be selectable.

Just to make sure, I found a post where the developer, Bastian Winkelhaus, confirms that an upgraded sponsors card in position 5 is worth 6. I've provided the link to the post below where he states: "The upgraded Sponsors action card will make it so that you can play 6 levels of cards (5+1)."

boardgamegeek.com/thread/2810762/sponsor-card-upgraded

What move #? Screenshot?

Sponsors II works as expected.