Can not receive WhatsApp messages unless I open the app
I just had this issue here with P10 - WhatsApp would not receive until opened or at least running in the background. Now it receives even if closed. I solved it by:
Settings &gt; Search for setting &gt; Ignore battery optimisation
If by 'Allowed' apps you don't see Whatsapp, click on the corner triangle for 'All apps', search for Whatsapp and 'Allow'