New Outlook Groups Do Not Appear in Outlook 365 Navigation Pane Upon Creation of SharePoint Site

Hello, all.

I have been breezing along fairly steadily with creating new SharePoint ('SP') Online sites. They seem to sync nicely with Teams and other programs, too. In the last 48 hours, though, I created ~5 new sites. The client "cards" do appear on their associated SP Hub site, and when I click on Conversations for each client within SP, it does direct me to the Outlook Group for each client card. But (unlike before) none of these five new Groups appears in Outlook on the left navigation pane. And none of them generated the usual Welcome to the [x] Group to my inbox.

It gets worse. My office manager reports that when she clicks on Conversations, she doesn't even get as far as me. She just gets her general Outlook inbox. So, I'm trying to determine if something has come across the Microsoft tech boards this week where others have experienced the same sort of thing. I can't even find an option to "regenerate" a welcome message to the inbox, and nearly all of the existing community threads assume that the Group is visible and simply requires editing. That's not me!

I have learned to try preëmpting the usual feedback to save time! So ... to be clear ...

1. Yes, I have "permissions." I am the owner of this small business of seven people and (effectively) my own IT department. There is no question of "permissions" for the rest of my staff, either, including the aforementioned office manager.
2. I created a checklist for creating new SP sites, and I follow it strictly. No deviations. That includes naming authorized members, assigning permissions, aligning the site with the appropriate SP Hub (I have three), syncing document libraries with OneDrive, altering advance library settings to open programs (such as Word and Excel) in their native apps, connecting the site to Teams, creating channels, reorganizing existing web parts to SP, and then adding parts (e.g. Calendar) that transport the user to the same Group calendar. I even have a set protocol for which menu items will open a new tab in the browser.

Bottom line, there is zero difference between the SP sites (pre-2024) whose Outlook Groups do appear in the navigation pane ... and the five new ones that won't behave the same. I changed nothing.

Last, I have replicated this problem on my MacBook Pro (M1) and Win11 (Corsair One) PC alike. So this is not a Microsoft vs. Apple hardware issue. The same issue also appears on my law partner's Lenovo (ThinkPad Carbon X1) laptop, so it bridges multiple devices on multiple platforms ... and regardless of user. Moreover, the problems surfaces regardless of new Outlook versus old, and desktop Outlook versus Outlook for Web.

Any insights beyond what I've already ruled out would be deeply appreciated!

Tom