Photos not opening in Photos app

Here is what I am running. I have a iPhone 8+, a iMac late 2009 running High Sierra and a mid 2009 MacBook Pro with El Capitan that was just given to me. When using the MBP and opening Photos, I see all my pictures there, even the ones I had just taken with my phone. But when I go to open them by double clicking, It opens up an exclamation point. It does not do that with all my photos, just some. I can open one or two in a group, for example if I took 10 photos of my daughter, one or two will open. It will open photos I have saved form the internet. It will play one movie I made in iMovie, but not the other one. Videos of my kids playing say "Photos cannot play this video. Do you want to try it in QuickTime Player?" When I click and hold to see the Live action of the Live Photos, it just turns burry blurry. I have already tried to repair the Photos Library by holding option + command and that didn't work. I also tried to reinstall a fresh version of El Capitan to no avail. I am kind of stuck on this short of going to Apple for help.