Try Whatsapp beta. Search in google " WhatsApp beta for Windows Phone 10" and click on any website of "wpcentral" and u will find link to download WhatsApp beta from Windows store.
WhatsApp beta have same problem. Click on WhatsApp icon its shows loading . Not opening application. It's problem starts march 3rd. My os version 15047 Lumia 730. I try many . Times hard & soft reset. Reinstall WhatsApp . Please helpe . And fix the problem
That is the latest fast ring build. You can either wait for a new build and see if that fixes it, meaning it is Whatsapp compatibility issue, or you can use WDRT to go back to the main production ring, where I am sure it will work.