Have you contacted Customer Support through this form and asked for the Pass Cover Number?

https://eurail.zendesk.com/hc/en-001/requests/new

Customer Support is currently overloaded with requests so you will probably have to be patient to get help. Please let Customer Support know what date your travel will start so that they can prioritise your request correctly.

For most routes there are different possibilities to make reservations and some don't require the Pass Cover Number.

If you give your travel details: date, departure time and route, here you can get advice on alternative ways to make your reservation. 

Yes I have raised a support ticket. 
 

I want to travel on the 7 June 

     1. TGV 8362 La Rochelle to Paris Montparnasse departing at 8:24am

2. THA 9339 Paris Nord to Bruxelles Midi departing 12:19pm

what options do I have to book the ticket?

also I see the price in eurail.com as $usd59.40 versus EUR40 in travel.b-Europe.com. Why is this different so large ?

Eurail.com have a reservation fee of EUR 2 per ticket so if there are 2 of you travelling that will explain the difference in amount. 

There are others in the community who are experts on reservations so you will get advice on that from someone else. 

TGV 8362 is 20€ per person.

Thalys 9339 Paris - Brussels is 25€ per person.

Eurail adds a booking fee of 2€ per person and train. B-Europe adds 4€ per order, which in this case comes down to the same.

Hi team,

I’ve not had any update on support ticket that I raised several days ago for the pass cover number. What’s the eta to get the details ?

Also, mentioned above, was that there may be alternative ways to book this journey.  What might they be?

You can also book by phone via SNCF. Press #85 for English, no booking fees, reservations are sent via e-mail.

I’ve been waiting for 9 days for a response to my support ticket for the eurail pass cover number. 

Haven't you booked via SNCF by phone yet? Neither trains you mentioned have 2 pass holder seats left.

The first available train from La Rochelle on 7 June is now the 10:44, arriving in Paris at 13:37.

The first available train from Paris Nord with 2 pass holder seats is the one at 18:25.

Don't wait if you want a seat. This is right after a long weekend, so it will be very busy.