Thank you for giving me a direction to think. The issue has now been resolved.
Since my phone interface was originally set to Traditional Chinese, the Enhance Pro app automatically switched to the Traditional Chinese version during installation. When my hearing aids had more than one program, the first connection attempt using the Traditional Chinese version of the Enhance Pro app would result in a connection error.
However, if the first connection was made while the Enhance Pro app was in English, the connection succeeded without any issues. After the connection was established, switching the app back to Traditional Chinese still worked normally without any connection errors.