Man
As an input I usually use Asio4All to record my guitar (which is not a native driver), but in jammr I can't find Asio option in audio settings. I tried different inputs, but I just can't hear my guitar.
Just as a thought, have you made sure the frequency of input device matches the frequency of your guitar input? Or that the frequency of both inputs matches the frequency of your audio output? I have built my own home studio and I run into this problem all the time when routing from different hardware inputs to software outputs. Even if your settings in Jammr are set correctly make sure your settings in your operating system are set this way too.
Also if you are using ASIO4ALL drivers you can still use it in Jammr (Unless there is some licensing problem I don't know about. ASIO4ALL is a universal driver and many competing commercial applications support and use this driver) The method can be rather complicated depending on your setup. If you use ASIO4ALL and have a hardware mixer or amp or something you can run through, output your ASIO sound to the hardware then route it back into your computer in a mic plug or some other input. If you do not have hardware, you can create a virtual audio interface to accept the incoming ASIO sound and route it internally in your computer to your audio input. There are many different ways to do the virtual audio input, personally I use my DAW to do it, but I have done it through freeware drivers, and I have seen other people use other setups.
Feel free to message me or email me, if you would like more specific instructions.
Good Luck!