Domain Name System Setup

I need assistance with a final DNS cutover that ensures that the .org domain email works exclusively in Google Workspace while maintaining compatibility for users that still utilize M365 for office applications.

Here's the background: We recently migrated our Microsoft 365 (M365) data to Google Workspace for nonprofits with the help of a volunteer. While the data migration was successful, we encountered challenges during the DNS record update phase.

Here's the current situation:

We have two domains

* The .com domain is fully set up in Google Workspace for Nonprofits and works fine.
* The .org domain is partially tied to Microsoft/M365 because some users continue using M365 Office applications but not for email.

All email should be routing to the .org domain (which may still be the secondary domain in google).

The issue:

I was instructed by our volunteer to copy and paste DNS records from M365 to Namecheap, our domain registrar, I did so without any detailed guidance, which may have introduced errors. Since then, the one user that was never migrated from M365 hasn't been able to access her email via her .org domain account. I suspect that the following are contributing factors:

1) The .org domain is still set as a secondary domain in Google Workspace (our original setup used the .com domain as primary)
2) Potential misconfiguration of MX records or other DNS settings in Namecheap (potentially in M365).

I'm autistic, and if the step by step instructions aren't clear, I'm just going to get stuck. I'm familiar with general DNS configuration, but I'm unsure about the sequence of steps. I expect that this can be solved in less than a half hour by walking me through the final cutover steps via zoom call/screenshare between M365, Namecheap, and Google Workspace.