Google Drive space is too low

Google (and Paperpile) claim I have 3Gb free but Sync is refusing to run with this error.

I’m loath to pay for Google drive for my personal account when I already pay for Dropbox and have unlimited Google drive through my institution (but I don’t think I can use that easily without making a new Paperpile account?)

We limit uploads if they go over 95% of the Drive disk space, so as to avoid filling up the disk (which would complicate things in the rest of the Google ecosystem). This limit is hardcoded in the sync code.

As you point out, syncing to your institutional GDrive would still entail opening a new Paperpile account and migrating there. Using a different account’s GDrive to sync will be possible before the end of this year – check out our roadmap.

Recently, I had to free up my G Drive space, so I transferred my Google Drive data to local drive data by using the Aryson Google Drive Migration Tool. It freed up my Google Drive space. It also has the option to migrate G Drive data to Local Drive, OneDrive, or another Google Drive account.
Hope it helps solve your issue.