DS18B20 library missing after adding to app

After adding the DS18B20 library into my application in the typical way, I get the following message
fatal error DS18B20.h no such file or directory
deleting the entry, library and re-inserting doesn’t change anything. What can I do?

What’s your typical way?
In what IDE?

Thanks for responding. I am using the Particle Build Web IDE
Before adding in the DS18B20 library, my code compiles fine. It also uses the Adafruit-SSD1306 library and a set of libraries needed to use the SparkFunSX1509 multiplexer (Arduino versions from gitHub added via the + sign). Then I go to library, search thru the community libraries for DS18B and add that library, clicking on include into project. It adds the include line in the code, but when I try to compile I get the no such file or directory error message.

It is now working.When using the following I get the error,
if (useTemp) DS18B20 ds18b20(D2);
but it compiles fine if I use
DS18B20 ds18b20(D2);

Certainly the error was mine, but I don’t understand why it would give the file not found message

this will seem crazy , nut the error is back once again and I cannot make it go away

Can you share your project?