Michael Rudolf
Premium
@Reiche try unsubscribing and resubscribing the content in Steam. It happened to me a few times recently that for some reason Steam wouldn't update workshop content automatically. I found it's a bit "hidden", you have to go to your Steam profile, inventory, rFactor2, then click on the content and "show workshop item"Oh that's weird.. I did already connect after buying the pack to check if I'd be ready to join!
Maybe you're suffering from the "your content is updated but it's not really updated because you have an older version that's not the older version of the server".
I remember this bug happening to some people basically every week when I raced the GT3 races 1-2 years ago.
I'm sure some of the rF2 regulars can help you how to check that! It's something about the content history not being the same, probably because either the server or yourself have skipped some content versions.