Question:

After updating Samsung Notes to the latest version, why can't I install the Samsung Notes add-on due to an error about an unknown source?

Answer:

Samsung has identified this issue affecting some users using Samsung Notes V4.0.03.28, and they plan to release an updated version soon to fix it. To avoid such issues in the future, please keep your device's software and apps up-to-date by checking for updates regularly through FOTA (Firmware Over The Air). As a temporary solution, follow these steps to allow installation from the current source:

1. When error popup occurs, please tap Settings

2. Enable the option "Allow from this source."

By doing so, you'll be able to successfully install the Samsung Notes add-on and use the app without any problems.