Photos app showing ‘Client Request Library Rebuild’ error on MacBook Air

So, can you tell us a bit more?

• When you say "iphotos on my mackbook air," do you mean the iPhoto app that was discontinued 10 years ago, or are you referring to the Photos app?
• What year is your MacAir?
• Are you actually using 10.14.6 Mojave? I think that Mojave was the last Operating System to support the iPhoto app.
• 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?
• How much free storage do you have on this Mac?