How do I resolve a photo syncing issue between my MacBook and iPhone?

You didn't give us much information to work with.

• What "settings are you referring to? What does your Mac's Photos say at the bottom of the Library? Like this"

• What model is your phone?
• What iOS does it use?
• Are you using iCloud Photos to synchronize your devices? or what?
• Do you have “Optimize Storage” checked in Photos’ Settings
• Do you see all your iPhone pictures at iCloud.com?
• Do you see all your Mac pictures at iCloud.com?
• Have you checked to see if the Apple Account is really really the same on the Mac and on the iPhone and at iCloud.com?
• Where does your Mac's Photos Library reside-- in the Pictures folder of your internal drive, or on an external drive? or on a network? on iCloud drive?
• Do you have more than 10% free storage on your Mac?
• Do you have more than 10% free storage on your iPhone?
• Do you have more than 10% free storage on your iCloud account?
• Has this problem always existed, or did it just start? Can you think of anything that changed that might affect your device?

Have you tried

• restarting your Mac?
• Forced restarting your iPhone?

Force restart iPhone - Apple Support

Let us know this information to help us help…