Sending to Distribution Groups

I'm trying to do some testing with the Sophos Email Gateway integration with Google Workspace for our organization. Things have been going well but I'm having trouble getting it to work sending to email groups. 

I added the group in Sophos and made sure to select distribution group when creating it. This matches the email of the group in Google Admin.

I've confirmed in Google admin that settings are correct to allow external senders to email this particular group.

I know that MX records and additional settings are correct because I can send to individual mailboxes without issue.

In Sophos Email Gateway, I can even see in the message history log that an email came in to that group and was delivered successfully. However, nobody in the group is seeing the email that is sent, so clearly it is not delivered successfully. Any help would be appreciated, I can't figure out what I'm missing.