Please see the following and try the appropriate solution.
(1) Are notifications about Pokémon and PokéStops turned off?
(2) Does your smart device meet the operating system and OS version requirements for the Pokémon GO Plus +?
(3) Is the battery of your Pokémon GO Plus + low?
(1) Are notifications about Pokémon and PokéStops turned off?
Please check if notifications about Pokémon and PokéStops are turned on in the settings of Pokémon GO. If they are not, please turn them on and try again.
How to turn notifications on
1. Start Pokémon GO, and tap the Poké Ball icon at the bottom center of the screen to open the menu.
2. Tap the gear icon in the upper right to open Settings.
3. Tap Pokémon GO Plus + in the settings menu.
4. If the boxes to the right of Nearby Pokémon and Nearby PokéStop are not checked, please check them.
(2) Does your smart device meet the operating system and OS version requirements for the Pokémon GO Plus +?
The Pokémon GO Plus + may not work properly on smart devices that don’t meet the operating system and OS version requirements or on certain devices that haven’t been verified for use. (Note: The list of verified devices is not public.)
Note: Even if your smart device meets the operating system and version requirements, and even if your device has been verified for use, the Pokémon GO Plus + may not work properly because of the smart device’s operating environment. Please be aware that we do not guarantee that the Pokémon GO Plus + can be paired with all devices.
(3) Is the battery of your Pokémon GO Plus + low?
If the battery of your Pokémon GO Plus + is low, please charge it and then try again.
Note: Please see here for details about how to view the battery level on the game screen and your Pokémon GO Plus +, and how to charge your Pokémon GO Plus +.