Good afternoon Atcandela,
Welcome to the Apple Support Communities!
I understand you are having issues syncing your photos with iCloud Photo Library between your iPhone 6s Plus and your Mac. Can you provide us with a few more details about your situation?
- What Mac computer model do you have and using what operating system? (Click on the > About This Mac).
- What version iOS is running on your iPhone?
- How many photos do you have on your iPhone?
- From your Mac, when you open Safari and go to www.icloud.com - How many images are showing? Do they match what is on your iPhone or what is on your Mac?
- On your Mac, did you turn off iCloud Photo Library in the iCloud settings, or did you log out of iCloud completely (for all services)?
Generally speaking, if the operating systems are up-to-date on your iPhone and your computer, and you have iCloud Photo Library enabled on both devices, then the photos should sync between the three locations. The time that it takes is dependent on the number of photos and how fast your internet connection is.
If you turn iCloud Photo Library off on your Mac, and then turn it back on, you will be uploading your entire Photo collection again, which may take a long time, depending on the size of the library. You can tell the status of the upload on the Mac by going to Photos and choosing the Moments tab. If you scroll to the bottom of the Moments collection, you will see if photos are still being uploaded.
Get help with your iCloud Photo Library
Here is some information about iCloud Photo Library. When you get a chance, reply to this thread with the additional information requested, and I'll do my best to help you!
Take care.