iPhone SE won't open Google Drive doc on google sheets or doc apps, how to fix?

Hello,

I have an iPhone SE which is fully updated.

I have the Google Drive app, along with Google sheets & docs apps too.

Google Drive is successfully synced with the account I would like to use, and I can see all the files & folders on the Drive app.

However, when I try to open a file, it redirects to Google sheets/docs & then I get a message saying that it can't open the file I want, and do I want to sign in with another account.

If I try to open a file from within the Sheets/Doc apps, it tells me I have no files saved.

I've checked and I am definitely signed in with the right account on all these apps, and still I can't open any of my files.

How can I fix this please???