I'm not sure if this is the right forum to post this, and sorry no screenshots, as I just realized this myself, and I don't want to re-create the problem just to post a screenshot.
But when I run the registry cleaner AND remove stored passwords using CCleaner (so not sure which one does this), the cloud icon for OneDrive in the systray continuously says "signing in" (when the machine is restarted), and when clicked on, and my account email is entered in the setup screen, it (the OneDrive icon in the systray) disappears and the OneDrive folder on my computer opens. Also, then no more syncs occur with any files on my computer and the cloud.
This caused me great frustration until I realized a workaround: to uninstall OneDrive on my computer (version 19.070.0410.0007) and then re-install it using OneDriveSetup (which you can either download or find on your computer somewhere assuming you have windows 10). I imagine this process then re-creates the necessary registry key(s), but that's just a guess.
This is an annoying workaround though because it then re-loads all my files again onto the cloud (over 25,000) once reinstalled from the setup file (even though they are there already), so it takes a bit of time to get back in sync.
So also, until I hear any solution to this problem, I guess I won't be deleting any registry files with "onedrive" in its path, and also no more deleting stored passwords. Because one (or maybe both) of those things causes this problem.