You can use the service of Belgian Rail for domestic TGV´s within France :)

From Turckheim you can catch a TER in Colmar to Strassbourg or Muhlhouse and catch there a TGV to Paris :)

https://travel.b-europe.com/Eurail-GE/en/booking-tgv#TravelWish

I still find a few trains that can be reserved, via the interrail website, for 1st class. Not sure if you are traveling 1st or 2nd class. But be sure to take a good look at the interrail website.

Otherwise follow the tip of @seewulf 

Thank you both.  This worked, but now it’s saying my Pass Cover Numbers aren’t working.  This is getting difficult.  

More information please! You say it worked?

What's with the pass cover number?

Thanks, Sven.  I private messaged Nanja, and she got me a new number.  On paper copies, there is a pass cover number.  On the mobile pass it’s called the Pass Reference Number.  However, to make seat reservations, you need this number.  Mine don’t work.  After browsing questions here, it appears it’s not an uncommon problem.  She issued me a new number to use.

I’ll keep you posted.  Going to try to go in and book shortly.  :-)

Hello Jenny,

I am having the same issue and whenever I book any seat reservation it says that my number is invalid. Messaged Eurail so hoping they can help me fix this issue. 

Hi Kdejesus, I think you mean the Pass Cover number. Just to clarify, with the Paper Pass you'll get a Pass Cover number. With a mobile Pass you don't. Through our self service reservation system you should be able to add your mobile Pass and make reservations without needing a Pass Cover number.

If you are booking with the train carriers directly, it is sometimes required to fill out a Pass Cover number. To ensure you can still make the reservation when you have a mobile Pass, you can request such number with Customer Support of with me via a private message (if you provide me with your ordernumber starting with IN or EN). 

I just provided you with the Pass Cover number, kdejesus, via private message.