I heard back from our developers, and it looks like this issues stems from not sending invoices directly from Harvest. It sounds like you might be copying the web invoice link and sending that to your clients, then marking the invoices as sent manually.
The problem with this, is our Stripe integration relies on a Sent invoice to generate an email address to be used for payment. This is compounded by the fact that we have per-user invoice links now. The invoice link you’re copying is from your own account, and when someone else visits that link, Harvest think it’s your email address viewing it.
To fix this, you’ll simply need to send your invoices directly from Harvest normally. If that’s not the case, let me know and we can take a closer look!
So, if you use Harvest, I guess you shouldn’t do that.