When using Export PDF to DOCX API, code hangs on exportPdfOperation.Execute method

I'm writing an app for visually impared person (I'm using the .net SDK for a Windows Form) that needs to have a many PDF documents converted to docx.  The app iterates through a directory, find all files, and converts those that are PDFs.  I've been testing this with a max of 20 files. Most files are around 500 KB and, for testing purposes, I added a PDF document from a scanner, that is 2 MB (the biggest file of all).

These files all convert individually. However, when I ran my app, the API hangs after about 4 of the small files (sometimes even after 2).  I'm using a trial account, which I believe has 1000 documents. When I check how many I have used, it's always stuck at 19 docs....like doesn't matter how many times I run my test winform  apps, the APIs call don't make it to Adobe. I get no response, it just hangs.

Is there some throttle with trial account? Is there somewhere a log I can see what's going on? I also did some search for batch exports, but couldn't find anything. Any help would be appreciated.