after iOS 26.2.1 update Bold Voice app is not working

You need to contact the app developer of the app if it isn't working as expected. Apple doesn't own the app, so they have no control over the app.

The first thing I do is delete the app from your iPhone, then go to App Store and redownload it (it would have a cloud icon next to it). If it still doesn't work, you need to contact them for help with their app.

Have you deleted the app and reinstalled a fresh copy from the Apple App Store? Have you talked to the apps support team? They might have some insights and be aware of bugs in their app.