Thanks for implementing this. I can confirm the basic functionality works. I get valid translations back from the API and they appear ingame. Unfortunately, there's a problem.
After about 10, captures, the capture functionality softlocks. GameTranslate doesn't crash (no crash report prompt), but no more text is captured. I can select a new capture region, but no text is actually captured when I do. This happens in both Internal and Attached modes. I tried it three times just to make sure it's reproducible, and it happened every time. Switching back to the internal translation model fixes the issue.
I did try reproducing the issue after turning on debug mode for the tool, but I don't know how to get the information you need to investigate. I expected debug mode to write a log somewhere in GameTrranslate's folder, but I don't see anything obvious.
If you need me to do anything on my side to get a fix going, let me know.