Cannot sync Google Drive between MacBook and iPhone app

On my iPhone I installed GoogleDrive 'Drive' app.

On my MacBook I installed Backup and sync from Google.app, which has created a ~/google-drive/ folder.

I have set the account to [email protected] and put some files and folders in it.

On my iPhone app I also set the account to [email protected]. I can see some of the older folders. These appear to match that on my MacBook, although the contained files are out of date. I can also see a file dated about a week ago which I have since deleted on my MacBook.

Files I have added/removed within the last 24 hours on my MacBook simply don't register on the iPhone.

It seems clear that the devices are out of sync. But they're both connected to my apartment's Wi-Fi.

I can't find any sync button / menuitem.

This is very frustrating.

What is going on? I was hoping that Google Drive would be my solution for distributed storage.

EDIT: The Google Drive web-app (Chrome -> drive.google.com/drive/u/1/my-drive) does sync ok with my macbook. Which suggests an issue with the iPhone Drive app, maybe?

Just clicking on Search drive in the app was sufficient to jiggle something loose and sync cloud -> iphone.

I noticed one glitch. The iPhone Drive app was failing to display bar.txt which IS on cloud (I added it yesterday), but instead was still displaying a foo.pdf file that longer exists on the cloud (which was showing up even before I asked the question), and bizarrely clicking on foo.pdf actually shows the contents of bar.txt.

Reinstalling the Drive App resolves this.

EDIT: I can recreate the problem as follows:
- On my MacBook I copy X.txt to ~/google-drive
- Observe that the cloud icon in the tray does sync animation
- Observe that X.txt does not appear on Drive app
- Drive App -> Search drive for X.txt
- Now it is visible