Sorry that there's an issue here, just some questions...
What is your primary phone?
What is your secondary phone -- and is that one running the DIGITS app or is it using a duplicate SIM?
If either of them respond individually do you get the text messages?
Has this been consistent or did it just start happening now?
Knowing this will help get us started if there is a known issue you're running into or if there is something more serious that we need to investigate.
Thanks for helping out with the DIGITS beta!
Primary Phone is Nexus 6P
Secondary phone is LG watch sport - digits duplicate SIM
Direct text to my primary number - received on Primary, duplicate SIM, Digits web app
MMS text direct to primary number with image - received on primary, duplicate sim, digits web app
Group Text with text only - Received on Primary SIM, Secondary SIM, Digits web app
Group text with image - recieved on duplicate SIM, Digits web app MISSING FROM PRIMARY SIM
The issue that is replicable seems to be the group text with image.