Issue after disabling iCloud photos on my Mac for a moment and then restarting...

My system library is on an external drive. It is beautifully synced with iCloud and has been for some time.. both libraries are identical and work seamlessly.. I shut off iCloud because I wanted to check on the condition of a system library backup I have on a different external drive.. Just wanted to see if it opened and worked.. (there are other reasons, but I'll spare the details here...)...

To my dismay.. It seems as if iCloud has no idea what's going on and that it was simply turned back on and need not do a single thing.. It's acting like it doesn't know the drive and library it's been working with all this time.. It wants to reload the entire library to my Mac when the library is already up to date. There isn't enough room on the drive to add all the pictures because all of the pictures are already there. What gives.. how can I start iCloud photos sync again and wake iCloud up so it knows everything is cool and it doesn't need to do anything? thanks in advance.. sorry for being so wordy.. long day... ("your full resolution photos will not fit on this Mac.." they are all already on the Mac.. more specifically the external drive that has the library that is designated as the system photo library..)