iCloud limit exceeded after moving Photos library to external drive
My Photos library is stored in iCloud (with a full copy in my Mac). I recently moved the Photos library on my Mac to an external drive to save disk space. I restarted Photos from that new location and designated it as System Library. When I went into Preferences to say I want to use the iCloud library, I get the message that I don't have enough iCloud disk space. This makes sense, as the same photos I have before I moved the Photos library locally, are still stored in there and count for the disk space used.
However, I can't proceed unless I upgrade to a more expensive plan. Which doesn't make sense. Why can't iCloud recognise the fact that this is the same Photos library, that has only been moved locally ? When I access the iCloud library on my iPhone, all is still working well and synced to iCloud.
Any suggestions ?
thanks
iMac with Retina 5K display, macOS High Sierra (10.13.1)