Trying to reestablish the connection from my iMac to iCloud

Make sure the file size you ever uploaded should not exceed 50 GB as explained in the article https://support.apple.com/en-us/HT201104

Read this article https://support.apple.com/en-gb/guide/mac-help/mchlp1774/10.14/mac/10.14

The uploading of files will take time if iCloud storage space is short .

Upload files to iCloud Drive to save changes made offline

You can upload files to iCloud Drive from a Mac or PC by doing one of the following:

• Drag files from either your desktop or a folder window on your computer to the iCloud Drive window. You can also drag your files to a folder icon in the iCloud Drive window. If you drag to a folder icon, it's highlighted to confirm that the item you're dragging goes into the folder.
• Click the iCloud Drive upload button  in the iCloud Drive toolbar. Select the files you want to upload, then click Choose.

If you don't have enough space in iCloud for your upload, upgrade your iCloud storage or manage your iCloud storage to free up space.

These were the files that were uploaded in the past date / time and the size of file is also mentioned and they are uploaded completely , the up arrow shows an indication of uploaded files ( that were created using some apps ) .

When you add your Desktop and Documents to iCloud Drive, all of your files move to iCloud and any new files you create are automatically stored in iCloud too. Then you can find your files on all of your devices.

They are shown in location > finder > documents , also you can open www.icloud.com with credentials , double click the document folder can you see old uploaded files in it .

See the article https://support.apple.com/en-us/HT203052

You must turn on iCloud Drive , see the section Turn on Desktop and Documents in the article https://support.apple.com/en-us/HT206985

As iPhone and Mac are signed in with Apple ID and password on the same network the files will again sync to Mac .

Regarding iCloud Drive ( archive ) folder the files will get saved when Mac is not connected to iPhone / synced .

In that scenario you have to uncheck the box of iCloud Drive .

open system preferences > iCloud and uncheck the box of iCloud Drive a pop up window appears , showing to keep a copy of documents , and remove from the Mac .

( a ) if you had clicked on keep a copy , they will be archived in home folder that can be viewed by clicking on finder in the dock , take cursor on top menu bar > Go > Home > your user name > iCloud Drive ( Archive ) .

Again double click on empty iCloud Drive box it will show setting up the complete files will start syncing from icloud server .

You also inquired if you sign out Apple ID from system preferences in Mac OS catalina 10.15.6 the issue persists , sorry I can explain in the next post how to configure ( sign in again with same Apple ID and password with screen shots ) and once again sync files using a single Mac OS catalina 10.15.6 that is set up with 2FA , as there is limitation to add massive words .