Line tracking sensor programming

We recently converted in class to the V5 system and are using VEXCode to program them. Here’s the problem I’m having…

We recently converted our robotics classes over to the V5 system, and are using VEXCode (blocks) to program them. I’m having my students program their robots to follow a dark tape line on the classroom floor. Each robot has one of the older, red (V4?) line following sensors that the students will put on the front of their robots. I have currently programmed mine the way I thought would work, so the sensor is outputting a “reflectivity %” value. The problem I am seeing is that the value does not change when moving from light to dark, but it DOES change when I move the paper closer or further away from the sensor.

I’ve put a piece of dark blue duct tape on the paper that we are using to test the sensor.

My program is as follows, in VEXCode blocks:

Begin Forever loop
If LineSensorG reflectivity in % > 18 then
stop FR
stop BR
spin FL forward
spin BL forward
stop FL
stop BL
spin FR forward
spin BR forward
(end If/else loop)
(end forever loop)

In the program, LineSensorG is the line tracker sensor. FL is Front left wheel, BR is back rear wheel, etc.

I’ve tried adjusting the height of the sensor above the floor (and paper) with no positive results. I’ve changed the value of reflectivity on the sensor with no luck there either. Again, the value does not change when moving from light to dark, though it DOES change when moving the sensor closer or further from the test object.

I want to be able to make this work, with the V5, with the sensor, and with VEXCode blocks. I have been able to make this work with RobotC and the older Cortex system, so I know it should work in this system. What am I missing; how can I make this happen for me and my students?