Hi Jessica. I also PM'd you, but for the benefit of the community I'll put the short version. In my experience this is often caused by a combination of settings. If you set Email Addresses in the support contact page at  Site administration / ▶ Server / ▶ Support contact, then many of Totara's functionalities will attempt to send email as that email address. The problem is that often times, the IP address/server where the LMS is running is not permitted to send email on behalf of the domain set within those settings. Those permissions/policies are typically managed with DMARC (domain keys and SPF policies).

I would suggest enabling the setting at Site administration / ▶ Plugins / ▶ Message outputs / ▶ Email to "always send email from the no-reply address"  (this recommendation is under the assumption that the no-reply email address IS permitted per DMARC policy to send email from the server/ip-address where the LMS is running)

Jamie