For some reason when i edit tag of already upload picture on my laptop, the save button do not working no matter how many time i click on it. I can only edit tag by using my iphone.

But the save button DO working

For some reason it only working on my iphone but not the laptop.

is your iPhone on wifi or mobile data?

what browser (& version) are you using on your laptop?

My iPhone on wifi while my laptop use Google Chrome 59 , Windows 8.1

I presume you are logged in on your laptop OK? try logging out and logging in just to be sure.

First thing to try is disabling any script blockers or ad blockers and see if that's blocking the save changes.

Try another browser like firefox and see if it's an issue with chrome, if so you can try clearing chromes cache files and cookies for this website.