Re-enabling iCloud Photos on 2014 MacBook Pro

I had iCloud Photos set up on my 2014 MacBook (The model is irrelevant)and it was working fine, but I had to disable it for a few days. I want to re-enable it now. So, I entered my Apple ID settings in system preferences, found Photos in the list, and clicked the checkbox. Simple right? No. It's asking me to buy 6TB of iCloud Storage. It won't let me switch which plan, and besides, I'm not going to buy more storage anyway. I'm currently sharing a 2TB plan with the rest of my family and my iCloud photos library is already contained well within that subscription. I have access to it on all my other devices on my Apple ID, but for some reason, every time I check the iCloud Photos box on this Mac, It requires me to buy storage. All my other iCloud services are working correctly, and within my family-shared iCloud subscription. Does anyone have a fix? Please help!