Hmmm…I am suspicious of Dropbox. The link you gave doesn’t apply because my Dropbox Folder has been relocated to ~/Library/CloudStorage/Dropbox, as in this thread. Smart Sync is no more, instead you right-click on files and folders and select “make available off line” or “make on-line only”.
I had already done “make available offline” for the top level folders of my databases, but the reason I am suspicious of Dropbox is that I drilled down to one of the dimmed/unsyn’cd folders and did right-click/make available off line and DT3 immediately stopped showing it as dimmed/unsync’d.
However this has not worked for the other dimmed folders.
Another oddity is that in any DT3 dimmed folder none of the contents at file level have an unsync’d icon next to them …only the folder containing them.
This may be a Dropbox beta issue.