Combining two models

I created a model on my work computer and saved it into Google Drive. I tried to open it at home but it was having problems (probably because of my crappy internet?) so I created a new model and continued working.

Today I was able to open the first model I created, and I would like to combine the two, but the copy/paste command doesn’t seems to be working from model to model.

Is there another way to copy and paste from one model to another or combine the contents of the two?

To complicate matters the second model isn’t saving.

Excellent. Thank you.