Hi Andras,
I have tried the above to resolve it and still no luck. I was looking through the support form and I saw above mine someone else was having the same problem about payments being stuck in process, but I think they are using PayPal standard and I’m using PayPal pro. Kinda happy and unhappy that I’m not the only one facing this issue.
I don’t think PayPal pro is the issue because it works perfectly fine for my other products on my website and they all say complete. Also just two days ago using your plugin it would complete payments.