Wikipedia says Viva.com is a multi-billion dollar startup

It 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.