Hey Michael, I hope this message finds you well and that you have resolved your issue by now.
I just saw your question and just wanted to drop my thoughts, in case you haven't.
From what you're saying, I think there is a good chance that your old template was running on 7.0, and the second you changed it to Brine you updated it to 7.1.
You can find the version info under "Website", scroll down to "Utilities" and you will see the version number at the bottom.
See the attached files for both options, 7.0 and 7.1.
If that's the case, I'm sorry to be the barrier of bad news but you can't go back from 7.1 to 7.0.
Unless you duplicated your website with an old template naturally you can just use that again.
Mirjam