The single country ticket is only valid in the named country. The German pass does allow some journeys into adjoining countries, but it is confusing whether it is valid to the border between Germany and Austria or specifically to Salzburg.

https://www.interrail.eu/en/interrail-passes/german-rail-pass

You may find it only valid on trains operated by DBahn so try trains at different times and see if it accepts them - the train you show is operated by OBB (Austrian rail).

Salzburg is a German Tariff point. ALL domestic network tickets valid in Germany are valid to Salzburg.

The website also confirms this:

https://www.eurail.com/en/eurail-passes/german-rail-pass

This means we have a bug here. Please report it here:

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

As a workaround, please add the journey manually (scroll to the bottom in the planner results, then tap on "Add it manually”) and put Salzburg in Germany.

@rvdborgt Is the German Rail Pass valid on all trains to Salzburg or could there be there trains where the pass isn't valid?

@HuawufromTaiwan 

The advice from the experienced travellers in the community is to not activate the pass and travel days in advance. Please read more about that below. 

Here is some useful information from the experienced travellers in the Community regarding both planning, reservations and activation of pass and travel days. 

 Planning

The rail planner is normally not up to date, as it only is updated once a month, so to be sure of the time table you better check the timetable and availability on the websites of the national railways. The bigger national railways, like DB (Germany) SBB (Switzerland) and ÖBB (Austria) cover several countries. 

 Reservations 

The information page on the eurail.com does not limit validity to Salzburg to certain trains only.

In practice the only by now trains that on THIS sector do not take pass is WESTbahn-which has 3 or 4 ttrips extended to/fro M on its route Sbg-Wien. It does not matter what is written outside on the trains, as for this sector it is DB and from Sbg onward it will be OeBB.

There MAY be however restrictions on local pax for this sector for an odd train-if there still is, most likely the NIghttrain to SLO etc.

Same issue is for Basel on SNCF, or even Basel BAD which is IN Swiss but also a definite DB tariff point.

What is your source? According this information, The German Rail Pass is valid between Munich and Salzburg:

Westbahn runs as Westbahn, not as DB or ÖBB.

I can only find Salzburg (Austria) and no Salzburg (Germany) - so what to do if I want to book Salzburg - Munich ? 

If you with "book" mean that you have a German Rail Pass and want to enter a journey between Munich and Salzburg, then you follow the advice above and enter the journey manually putting Salzburg in Germany. 

I live in austria - for austria i have the klimaticket - for the rest of austria I have the eurail - pass 

i could travel via Passau to Frankfurt (Germany) - but I seems I cannot travel via Salzburg to Munich 

there is no Salzburg in Germany - but Salzburg (in austria)  and Passau (in Germany)  are counting in austria and Germany as a border railway station 

I live in austria 

for austria i have the klimaticket 

for Europe I have eurail pass 

If there is no Salzburg (Germany) simply add the train manually. Scroll down and dou should find where you can add it manually.

Abou your pass. If you live in Austria you need an Interrail pass and not Eurail (for non european).

Chiasso also exists only once but it does work for the One Country Pass for Italy (that was in October). Don't know how it works for a global pass with Italy as a country of residence.

I'd say: try to add a journey from Salzburg and see if the question comes up whether you want to use an inbound/outbound journey. If it comes up, then you need to enter the train manually. If not, then it should work without using an inbound/outbound. Test with a future date, so you can cancel if needed.