I assumed that the flow was giving error when you are running it.
I take that for some of your users this is working fine, while not working for a few users - is this correct?
Sharing OneDrive folder is not an issue. You don't have to share that, because OneDrive connector will use User's OneDrive and create PDF file through it.
For the user who is getting this error, most likely they changed their account password and that is when the access token expired.
If your users are initiating the cloud Flow from Power Apps, then can they (who changed their password) reload the Power App so that they see the initial permission screen (consent pop-up)?
Alternatively, can you make this a feature App within your organization so that nobody see the initial permission screen (consent pop-up) when they open the Power App - this way user password change will have no impact on the access token. See https://www.o365dude.com/2019/01/06/bypass-consent-pop-ups-in-powerapps/ for further information.
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