What a strange question.

Interrail flexi passes are relatively simple - you can travel across Europe on any 4 travel days in a month. However you can only use them in your country of residence on 2 of those days. These are the inbound and outbound days (but they are poorly named since the only control is whether you had any journeys in your own country on any of your 4 days. There is no requirement to cross any border so you could use them to get to a German airport.

Your remaining days can be used for unlimited journeys on those days in any of the remaining 32 countries in the scheme.

Any further  travel days with journeys in Germany would have to bought from the standard ticket office. If you try to add one to your pass you get a warning.

What is your country of residence? What type of pass do you have?

If you are from the US then you should have a Eurail pass and Eurail passes have no outbound/inbound travel days.

I have an Interrail Global Flexi Mobile Pass. It’s good for 4 days within one month and we purchased it from Germany. So far we used it to travel to UK and back using the inbound/outbound. I thought we still have 2 travel days left on the pass but appartently not. I don’t understand how I can use the remaining two days. Are these not designated travel days? I’m planning to travel within Germany, not crossing the border. Do I have to let them simply go? 

That is against all rules-or do you actually LIVE here in DE-this mask wearing island? Where did you buy it?

But its now to late to exhcange pass-you can still use remaining days OUT side of DE-and can use-with careful planning the dirt cheap 9€ ticket to get to most borders to cover the DE part

Yup we live here in the mask wearing country. Which is not an island btw...In any case, I did not understand this particular rule about the use of remaining days not being allowed inside the country where you bought the pass. Does anyone else know a way around or is this it? 

The whole idea with Interrail is to explore other countries than your own. For many years you were not allowed to travel in your own country at all with the Interrail pass. Then you only got a discount on the travel to/from the border.

At present there is the outbound/inbound rule that allows you to travel on a maximum of two travel days in your country of residence.

As you already use your travel days in Germany you can't use the pass in Germany any more. 

If you want to travel in Germany you can use the 9 EUR ticket throughout August.