I would also try speeding up the movements of the robotic arm to see if that has an impact, also make sure the Workcell is stable, if it is sitting on an unstable table it may affect how it draws the lines.
Here is a video of the robot performing a joint move followed by a linear move
My students are also unable to draw the linear path with the workcell in lab 4. We have 2 workcells, and neither has been successful with the straight line. Both draw arcs for both the joint and linear movements. Oddly enough, the linear movement begins and ends the path in a different location, even though the coordinates are not changed. In effect, the arcs are like arcs of 2 concentric circles with different radii. Your video is now unavailable, by the way.
Hi @brigittegudz! Check out this article, FAQ of the V5 Workcell. Firstly, try the question number 3. If you have done this and are still seeing no difference, follow the rest of the troubleshooting steps. Also, feel free to share any video you have of your Workcell operating!