There could be a number of reasons for this. Keep in mind that Walabot DIY works with most phones operating Android 6.0 or above and must have USB OTG support. Additionally, the Walabot DIY is not compatible with iPhones, computers, or tablets.
On some phones, it is necessary to manually enable the OTG (USB On-The-Go) feature.
For most phones, this can be done by going into the Settings of your phone and then Advanced Settings, and then OTG Storage. Alternatively, you can search for OTG in the search bar of your Settings. [Note once your OTG is enabled, it may turn off automatically after 10 minutes of inactivity or if you leave the Walabot app.]
If your phone's OTG is enabled and it is still not connecting to the Walabot, make sure your phone is running the latest software version. You can check for app updates by visiting the Google Play store and going to the Walabot DIY app page. You can also update the app by uninstalling it and reinstalling it.