I suspect that Google going out of their way to make this required had a very reasonable and thought-out process, while the sender's omission was on oversight, so I haven't contacted Google Workspace support.
replyWhat's truly iffy is that GMail doesn't have the same strict requirements, and there's no way (at least that I found) to turn it off for my Google Workspace domain.
Wikipedia says Viva.com is a multi-billion dollar startup
replyIt seems unlikely you're the first company using viva.com and using google workspace.
Clearly the problem here is that viva.com emails aren't arriving on your google workspace, despite what their support process says.
viva.com emails do arrive on other email providers, so seems unlikely to be problem with your viva.com account
It seems unlikely workplace blocks all viva.com emails otherwise more than you would have complained.
Whether that's viva's problem or google's problem is a separate problem.