PII caution: Please note that this is a public forum for users. I have removed some private information from your question for your privacy and security.
Hello Thomas Silverwise,
Since the app stopped working immediately after its latest update, and Repair, Reset, and reinstall did not help, this is most likely a problem with the current app version.
Here are some suggestions you can try:
Create a temporary Windows user account under Settings > Accounts > Other users > Add account, sign in to it, and test the app there.
If the app works in the new account, the issue is likely limited to your original Windows profile. If it still closes immediately, the latest app update is more likely causing the problem. In that case, report the issue directly to Duckhead Software through its official HEICtoJPEG GitHub issue page.
Note: Although the report is submitted through GitHub, it is sent directly to Duckhead Software, not Microsoft.
When sending feedback, include the app version shown under Settings > Apps > Installed apps > HEIC to JPEG > Advanced options, your Windows version, and mention that Repair, Reset, and reinstall have already been tried. You can also ask whether the developer can provide a safe way to install the previous working version while you wait for the fix.
Disclaimer: Since this is a third-party app and this is a user-to-user forum, we can only suggest general Windows troubleshooting. We cannot access the app’s internal systems or fix problems introduced by its update.
Hope this issue will be sorted out soon. Thank you for your patience!