How have you set up the settings in psychopy? The guide I mentioned ( Communicating with an Eyetracker — PsychoPy v2025.2.2 ), specifically mentions using the Tobii Pro Nano. Did also make sure to install the other required software? https://www.tobii.com/products/software/applications-and-developer-kits/tobii-pro-eye-tracker-manager#downloads
Did you try using an older version of psychopy (2022.2.5) as discussed in previous threads?( Iohub problem in eyetracking experiment (Tobii X3-120) - #2 by Damien ; Integrating eye-tracking with Tobii eye-tracker - #18 by mjohnston118 )
AFAIK there is nothing unique about the Nano compared to other products in their line in terms of calculations and event handling. Therefore, either it is not setup correctly, or you just need to try using an older version of psychopy.
Issac