Subscription doesn’t work
I paid for one year $69.99 and when I use the features on the app Im asked if I want the subscription. I thought I made a mistake. When I subscribed again the app shows Im already on a subscription. Ok. User error no biggie right? I try and use COMBINE PDFs and again im asked for payment.
I know this won't solve the issue with your paid subscription not working, but I wanted to let you know that the free version of Adobe Reader, when accessed on the web, allows more features to function than in the app. I was able to combine and/or rearrange multiple pages along with a few other functions as well.
Another place I found more cost free functionality like this was in the Adobe Scan app.
P.S. The actual website for Adobe Reader, not the Windows PC app. Although the Windows PC app does provide a very useful platform in its own right, I just wanted to be clear as to the specific function of combining files you had mentioned.
Hope this helps!