Munich to Budapest again (and thank you)

I don't know what your problem really is. I just looked up Munich to Budapest on the DB website and there are plenty of trains. Here is one close to what you want:
Munich to Budapest leaving 09:29 Planned arrival 16:19 Duration:6h 50min RJX 63From: München Hbf Gl.5-10 To: Budapest-Keleti
Total per person €55.90

Thanks Lifetime Travel. Much appreciated. If you go further in the booking process and/or try and book seats, you will see what the problem is and what I mean. Even OBB admits there is a problem unless it has been corrected since my receipt of its e-mail (today). Thanks so much for the effort. I just don't know exactly how to interpret OBB's response. It's not written well (as in communication) in English. Maybe if I send a reply e-mail, they will respond again more clearly. Not sure.

So what you do is buy the ticket now. Tickets now are cheap, and will only go up in price

Once you have a ticket you have a contract with the railway. They now must transport you from Munich to Budapest, come hell or high water. Railways cannot cancel tickets from their end, and cancelling trains does not lead to tickets being cancelled, as tickets are for a route, not a train. And that is even the case f you buy a discounted ticket, bound ot a particular departure, as then you still have a ticket for a route. The limitation that you stick to a particular train gets lifted if that train cancelled.

So buy that ticket, and let it rest for the time being. Do not overthink this. You buy tickets in advance to secure a discount, not to secure seats, as securing seats months in advance is never, ever, ever needed in this part of Europe.
A lot of people in this part of Europe buy their train tickets on the day of travel, and all hell would break loose if the railways suddenly told those people they could not travel when they wanted.
(When I mention to a German that it would actualy be a good idea if DB introduced included reservations with their tickets, like France and Italy do I get looks as if I just suggested I like to eat children...)

I really want you to relax. This is mass transit.

I would expect all Munich Budapest trains to still have seats available even on the day of travel itself. But if you want to be certain, reserve your seats a few days in advance. So there is no need to worry about this till August. I just had a look, and for example for today you can still get reservations for all direct trains from Munich to Budapest.
When you run lots of trains, like a good railway does, you only need about 30% of average occupancy to make a profit. So a good railway plans enough trains, so that even on normal days the trains do not get overloaded. The economics of railway operations is very different. That is why you will often find yourself on an almost empty train, and wonder, why is this even running? But the marginal cost of running a train is actually low. That is why you see so many lines running a hourly intervals. Railways buy trains based on maxumum expected loads, and run them the whole day, leading to many trains running lighly loaded.

So just buy your ticket, and wait till August, and then reserver. And I am pretty confident that you will be able to. What I think is happening is this:
Currently the Munich - Budapest EC services are operated using some of the older carriages that OBB still has in operation. These Carriages are perfectly fine (they maintained them well, and don't worry, they have AC). But OBB is currently getting lots of new trains delivered. And so they are gradually replacing older consists with newer ones, and cascading other stock down to other services. And because of that they cannot load seat inventory yet. As I mentioned in your other thread: The railways just don't know yet what train they are going to use on that service.

Thank you again, WengenK. I'll have to read this tomorrow morning to fully digest. It seems that perhaps I am making a mountain out of a molehill and my preoccupation with this issue has in part caused you to put in so much work in your fine (and probably time-consuming) narrative. My apologies. It's just my inexperience with trains and I'm in charge with trip planning LOL. In the times we have vacationed in Europe previously, we always rented a car to get around. Thanks again very much for this. Very much appreciated.

I received this message today from OEBB Customer Service:

Thank you for your message

This means that the train is not yet bookable.
 
It is not possible to estimate when this will be possible. Sorry about that.
 
It's best to check the connection regularly.
 
Have a nice Wednesday.<<

Kind regards