low recording level with guitar

I have a Line6 SonicPortVX as recording device, connected to the PC with a USB-cable. It has a direct input for a guitar sound cable.
Now that I have installed this with the latest driver, I tested recording my bass guitar.
I found that the recording level was very low. All pickups of my guitar were set to maximum level and the recording volume of the Device Toolbar was set to 1. I checked Windows settings and found they were at 100% (Windows - System Settings - Sound).
The amplitude in the Audio track showed maximum values of 0,05 in the scale ranging from -1 to 1.
My Sonic Port has no gain for guitar input, only for the microphone input.
Is there a way to get the recording level up?
Using Audacity 2.3.3 under Windows 10.

You are not the only one. There are many reports of this problem on the Internet (one example: https://line6.com/support/topic/4614-sonic-port-output-levels/).

The output level from guitars can vary massively. Some guitars with active pickups will produce close to “line level” (around 1 volt), whereas single coil passive pickups may only produce a few millivolts (similar to a dynamic microphone).

You can of course use Audacity’s “Amplify” effect to increase the level, but the downside is that any noise will also be amplified.

If you also own a bass amp, you may be able to take an output from the amp’s pre-amp stage and feed that into the SonicPort, though if you try that, start with the volume very low and take care not to overload the SonicPort.