This really varies per country and system. In general the answer is NO-not without any further acts you have to do. IF a country has only (fast) trains with obligatory REServation, you will have to exchange the now not able to use REServ. for a new one for the next train=&hope and pray that train is not fully booked. Some countries do that for free, others not. Do not moan: same rules will also apply to people without passes on normal tickets then. In most countries there will even be special desks/assistence counters for these cases. In fact IN the EU there is even a kind of law that the railway has to provide you with adequate assistence for these cases. But every country has its own interpretation on how to do that.
As an old time regular train traveller and having used some 20 IR passes through the years I kind of know which trains really must be reserved-and try to avoid these amap. I note that most newbees here do not seem to have the slightest clue and assume all trains have to-thats nonsense. The best thing is always to use the site/app of THAT railway where you are on then. Next best is bahn.de (german railways) as it has the best overall coverage and will tell if a REServ, is really needed or just voluntary.
The small comfort is that if you are able to gather at least 3 of such missed trains (delay >60 mins) then you can get a slight compensation at the end.
This really varies per country and system. In general the answer is NO-not without any further acts you have to do. IF a country has only (fast) trains with obligatory REServation, you will have to exchange the now not able to use REServ. for a new one for the next train=&hope and pray that train is not fully booked. Some countries do that for free, others not.
In case of cancellation or a missed connection due to delay, providing a replacement connection without any extra costs is obligatory.
In fact IN the EU there is even a kind of law that the railway has to provide you with adequate assistence for these cases. But every country has its own interpretation on how to do that.
The "kind of law” is called EU Regulation 1371/2007. Article 16 applies to missed connections.