Resolving erroneous network errors with personal vault

I appreciate there are many(!) general OneDrive vault issues floating around but I wondered does anyone have a solution to a very specific oddity which has rendered OneDrive useless to me - and hence is preventing me purchasing it for use with my small business.

Multiple Windows 11 PCs (all up to date, clean etc etc) - OneDrive working correctly, access personal vault and authenticate, all good can see files and access them.  One PC hard-line ethernet, the other via WiFi

OneDrive website - all working correctly including vault.

Samsung Galaxy S10FE Android phone (all up to date, patched, clean etc etc).  OneDrive app (v7.32.1) is working fine except for the vault... after authentication (PIN or Biometric I've tried both), the vault appears empty.  Upon refreshing, it throws a nonsense "not connected to wifi/mobile data" error.

Things to note... all devices are signed into the same MS account, I've tried different WiFi, just mobile data vs WiFi, I've uninstalled, rolled back to factory, cleared cache, reset app, logged-out and logged-back in again.  Nothing root'ed or custom on the 'phone, just plain android with Samsung setup.  I've confirmed definitely connected - as evidenced by other files upload and download fine, speedtest app shows steady 500/70 on the wifi.

Also tried the same version of the app on a cheapie Motorola android phone, exactly the same issue.

Can anyone help here - anyone else seen this?

I need to make a decision as to whether to subscribe for my SB but currently it's useless - the vault is primarily what we need.

Thanks in advance.