PC can not find BlynkSimpleEsp8266.h library

Hi guys,
I do not know what I did but since today my Arduino IDE do not compile the sketches what I write for little Blynk-Procects. I get usually the massage that the library BlynkSimpleEsp8266.h can not be found…
Until now I never get such an error… so I tried to deinstall and reinstall al required librarys which are written on Blynk-page “How to start” but there comes usually the same error.
Here the collocation from my librarys I reinstalled

I use Windows 10 with Arduino IDE 1.8.4
Were could lie the default. I hope someone can help me

Hello. If you haven’t closed and restarted the Arduino window since adding the library, you need to do that.