Rail pass reservations for these trains are no longer sold online by DB, so the booking options for rail pass users on these trains are:

• Book at a station in France at a 'SNCF boutique'
• Book at the Reisezentrum travel desks at a hauptbahnhof in Germany
• Or book in advance of your trip by using the Eurail reservation service or the InterRail reservation service but you will be charged a €2 booking fee per reservation.

A quick check on IR reservations is showing availability in both 2nd and 1st class.

Thank you for the help!

However, when I try to book using the Interrail or the Eurail websites, they show the following message: “Prices unavailable - No price results were found. Pass holder reservations may be sold out for this connection, but there are other ways to check for available seats - more info below our timetable.” 

Does this mean the train is already sold out? Or is there an error?

It can be so that Interrail only can sell these tickets as paper tickets and that the time frame until your travel is too short for a paper ticket to arrive.

 @rvdborgt @Angelo Do you know if Interrail issue paper tickets for the TGV between Germany and France?

TGV Germany - France is delivered as an electronic reservation by Interrail.

You can also call SNCF. Press #85 for English, no booking fees, reservation is sent via email.

For 23 August, it looks though like there are no pass holder seats left on this train. I get results for later dates, e.g. in September but not on 23 August.

IF it is possible to arr in P later in the day-you can also save a bundle too:

In DE this train is treated as ICE-RES is optional only. Can go as far as Karlsruhe.

Go to Strasbourg-change Offenburg-use local train at least last short part.

Use French/SNCF TGV from S to P: ev. hour and not well-known, so much more chance on finding spare seats-maybe still even for the 10€ in quota.

IF you do not really want to visit P but go home-south of FR-ESpana-PT: use other TGV from Str to the south of France-Avignon-Narbonne-Perpignan-and go with local/regional trains till Barca. Again a few blue notes saved.