We are fully vaccinated but due to Austria locking up will be landing in Frankfurt. The SNCF website says we are not allowed on the train without the Health Pass and I need to get into France to get my Pass? Will they accept out passport and vaccine cards on the Train?
This https://en.oui.sncf/en/help-en/coronavirus says that they should. Look at the part that says what a health pass certifies and how it is checked.
If you are spending any time in Germany, get theirs if you can.
One EU countries pass should be recognized in other EU countries.
Whatever you use to enter the Schengen zone, that will be your pass sanitaire or health pass.