Can be, this is a very common thing mentioned here. The planner on the app is NOT always uptodate. It is only updated every few weeks, and at the mo due to covid some companies adjust their timetable much more often. Others from far away do not even send their own data in.

You can book on the €* site and click some step in the booking on ´passholder´ or like that. You may even save the 2€ fee that Eurail charges as extra.

I am a senior having travelled by train extensively and never (maybe not yet) with the new mobile pass. It seems more+more young newbees do not grasp how the system works: In the past it was evident you had to go to a real station with people sitting behind counters to have those things done. You would pass them anyway when using trains. Can you imagine: there were not even mobile fones by then. EUrail is not a company, but a kind of coöperation between some 100+ different railways to attract people to train travel. But each and everyone sticks to its old, often very burocratic rulings on how to deal with tickets and REServations etc.

Happens actually quite often as Eurostar change the timetable according the actual travel restrictions The Eurail reservation service usually have atleast the guranted trains (that run for sure) but maybe doesn´t get the shortly added trains :/

Bestway to check is Eurail against b-Europe (here you can reserve aswell with a PassCoverNumber that can be recived from Customer Service in case you have a mobile pass) but here the Service Fee is 4€ instead of Eurails own 2€ https://www.b-europe.com/EN/Booking/Pass#TravelWish

I can second the point above about Eurostar making last minute changes. As Seewulf says, they’re being quite cautious at the moment, beginning with typically two scheduled trains per day in each direction and adding more as needed closer to the time.

However, there is also another, simpler factor as to why times displayed on the Interrail journey planner might not match up perfectly with those on Eurostar’s own site. That is that the Interrail timings include an allowance for the check-in time and border control, so that passholders understand that they can’t simply turn up and board as on any other train.

This is a very good idea, but unfortunately it doesn’t take account of the effects of Brexit and Covid on this process. The minimum time allowance is no longer the 35 minutes that Interrail indicate, but (according to Eurostar, who are understandably playing it safe) up to a whopping 120 minutes (for Brussels Midi/Zuid anyway).

I’m afraid this is no longer possible. Eurostar have an Interrail page, but clicking the booking link just redirects to Interrail’s own booking service (with the €2 booking fee).