Hello cynthiafromcave creek,
That behavior would be expected as only the System Photo Library can be used with iCloud Photos:
Although you can use multiple photo libraries in Photos, the System Photo Library is the only library that can use iCloud Photos and Shared Albums.
You can find that information in this resource: System Photo Library overview in Photos on Mac - Apple Support
To set your preferred library as the System Photo Library, you can use the steps below: Create additional photo libraries in Photos on Mac - Apple Support
You can switch to another library and designate it as the System Photo Library. For information about considerations to keep in mind when choosing the System Photo Library, see System Photo Library overview.
1. In the Photos app
on your Mac, choose Photos > Settings, then click General.
2. To make the current library the System Photo Library, click Use as System Photo Library.
Important: If you switch to another library, Photos automatically turns off iCloud Photos and Shared Albums. You can turn them on again in the iCloud pane of Photos settings. When you turn on iCloud Photos after designating a new System Photo Library, the photos stored in iCloud are merged with those in the new System Photo Library. After the content from the new System Photo Library is uploaded to iCloud, the libraries can’t be unmerged, so consider carefully before changing your System Photo Library.
Hopefully that addresses your inquiry.
Take care.