The .Nomedia file would hide any media from apps that are trying to access them.
For example if you have a folder of pictures and you don't want those pictures showing up in the gallery then you'd add a .nomedia file to the folder.
So if you want Google photos to detect your media simply remove the .nomedia.
If they still don't show up, try force stopping the app. If that doesn't help, rename the folder that has the pictures (you can change it back later)