This is not the first project in which I use firebase but this time I have found this problem. How can I solve it?
I have encountered this problem recently as well. It seems like a bug in Firebase. The good news is, it's simple to fix.
The contents of the file seems to be ok. I think it's only the file name that's been messed up. That's why I just renamed the file to
GoogleService-Info.plist and dragged it to the project as usual. And it works perfectly fine!