Yes.
The problem occurs when I want to make the initial purchase. When I try a second time, I get the message that the item is already purchased and at the same time I also receive the correct information from RevenueCat.
So the problem appears only at the initial purchase, after restarting the application it is ok.
Solved! Was my mistake.
After I deleted the project in RevenueCat and created it again, I forgot to create the offers too.
After I created the offers again everything works fine! @Alexander Stolte, thank you very much again!!!