Time Machine volume doesn't show up in "Browse Time Machine Backups"

I have had an external USB drive set up for Time Machine since I got my M1 MacBook Air. To reduce desktop clutter of having multiple external drives connected on my desk I recently bought a Synology DS423+ NAS, it currently has two 8 tb drives setup in SHR configuration.

I set up a new shared folder in the NAS for Time Machine. It appears to be working. When I go to Time Machine settings both the original USB drive and the new Synology drive appear. Both of them show that the latest backup is current for the day's date.

Before I disconnect the original USB drive I want to make sure that the backups on the new drive are working. But when I click on the Time Machine icon in the menu bar and select "Browse Time Machine Backups" it goes directly to my USB backup. I've done some searches on this I think that when I browse the backups I should first get a window showing the two volumes available which allows me to choose the volume I want to browse.

So my new Time Machine volume appears in settings but not in browse. What can I do to get it to appear in browse?