Hi, if you'll read your own posting a second time, you'll see that there are informations missing to give you a reliable answer:

Do you want to go this wednesday from London or do you just arrive in London this wednesday? Do you want to go to Munich via Paris or Bruxelles? Where and how are you trying to book?

For instance, this wednesday some trains to Paris from 14.31 on have available places in 1st class for passholders. 

But maybe you are looking for completely different dates or routes?

Where are you trying to book the London to Munich leg? (and what day? i found plenty of trains still bookable for 38€ per seat in 1st class)

You can reserve via Eurails own reservation service the Eurostar between London and Brussels and catch from Brussels a ICE via Cologne/Frankfurt to Munich :)

Munich - Paris is bestway reserved via a DB Ticket office one direct train per day at 6am

Paris - London is once more a Eurostar and will be 38€ in 1st class :) 

When I'm on the website with either computer or cell phone I attempt to book a reservation on May 26 after 4 (we land at Heathrow at noon) and it shows me routes but the portion from London to either Paris, Rotterdam, or Brussels says that I need a reservation yet even when they show me the fees, I have no active way of booking it. It's all grayed out and says that if I can't book a seat I will need to buy a full fare ticket. I have first class passes. I've been trying to book a seat for 6 days. No one replied to multiple emails other than to say once that they're busy and will reach me when they can. We have hotel reservations in Munich and everything will fall apart if we can't arrive before the morning of the 27th. It's the same problem trying to book seats going from Paris to London on May 30th. I don't know what to do but after spending $774 for 4 train rides, now a friend is telling me to fly instead. I'm an American teacher who wants to show her son Dachau and Paris but I've spent my money only to not be able to book seats. I miss the hovercraft. I've spent over 12 hours trying to arrange in advance and I've gotten no where. 

You did write “wednesday” before - may 26 is thursday.

Last available trains for 2 persons (as far as I did see):

may 25 - 17.04 to Bruxelles - next available train may 31 (17.04)

may 25 - 20.01 to Paris - next available train june 2 (19.01)

All other trains over the long weeekend have no passholder seats available.

Thank you for the information. I wrote May 25 because that's when we leave Los Angeles and won't be able to arrange reservations until we land on May 26. I imagine 6 days ago I could have scored seats but no one in the community or Eurail answered. Now it looks like I'll need to cancel all our passes and book flights. I'm so disappointed because my son has loved trains his whole life. I really struggle to believe there's no tech support when reservations appear on the website but the customer cannot book. Thank you for trying. You were the only one. 

I didn't see any message from you 6 days ago in this community.

However, you can still travel by train if you want. It's just that there are no pass holder seats anymore on Eurostar. Check e.g. https://www.thetrainline.com/ for fares.

I did write, and their response was that they're very busy. I'm confused about how to apply our passes when we book. Do I risk not getting a seat if I wait until we get there? I did a new search and they priced just one ride from London to Paris at over $600 for one ride. The same for returning to London from Paris. It's a $94 flight from London to Munich. Even less for Paris to London. If we book flights to be able to travel across the channel, we might be able to ride the train from Munich to Paris so he can ride the train at least once. How do I adjust our Eurail pass from 4 rides in 2 weeks to just 1? That could save us almost $600.

Ah, you wrote to customer service and not to this community.

Eurostar pass holder seats cannot be booked anymore via the Eurostar website. They removed that possibility. You can book via the Eurail website or e.g. by phone via Eurostar, or French or Belgian railways.

Eurostar is also very popular for citytrips during holiday weekends such as the upcoming one, so it's not surprising that all passholder seats are gone now and normal fares are getting high.

The minimum for a global pass is 4 travel days.

If you would like to do only one journey, then it's usually better just to book a normal ticket.

I think that the best for you would be to ask for a refund of your Eurail passes if they are refundable and fly from/to London and then purchase tickets for the train travel between Paris and Munich 

What does it mean “No pass holder seats?”  Does that mean we might still be able to take a train but not reserve a seat?

There is a limited number of seats for holders of Eurail/Interrail passes on some trains, like the Eurostar and the TGV. When all these seats are booked you have to buy an ordinary ticket if you want to travel with that train.

Is the site down? I’ve been trying to book and all it does is buffer. I have it on my computer and my cell phone, but my cell phone is getting a new battery installed and I tried using the app on my son’s phone and it wouldn’t let us enter our global passes in the app on his phone. It wanted us to block it on my phone. 

There are other ways to book than the Eurail site. Here is a guide:

https://community.eurail.com/train-connections-reservations-47/how-to-get-reservations-105

It is possible to phone SNCF (the French Railway)

https://www.sncf.com/en/customer-service/contact-us/telephone

 Press #85 for English, no booking fees, reservations are sent via e-mail.

Thank you everyone who has reached out with answers. We’re very grateful for your help in a stressful time. We bought a flight to Munich to avoid possibly not being able to land a seat at the beginning of the trip. I was able to reserve one booking but the site seems to be struggling and the above links ask me to click on “yes” and there’s a green “yes” button, but no matter where I click (cell phone, laptop, tower computer) nothing seems to happen with the “yes” button and I cannot advance through the site. We will figure it out as we go. I truly appreciate all of you who tried to help us out with great suggestions. You were very thorough.