In case a user fails to receive a share, first make sure that they are using the correct app.
For this verification you need to know the generation of your device, below is a guide on how to identify it: https://1control.zendesk.com/hc/en-gb/articles/360019566140-How-to-determine-the-generation-of-your-SOLO-
For 2nd generation devices, is required the use of the app
For 1st generation devices, is required the use of the app
Once you have verified the correct app installation, you need to make sure that the number to which you are trying to send the share is the same with which the recipient user registered in the initial configuration of the app, paying attention to any prefixes.
If the problem persists, do not hesitate to contact our technical assistance by writing an email to firstname.lastname@example.org