Error 81(Filament Jam Detected)
Error 81 is not necessarily an error, but rather the message that will appear when filament stops moving through the Smart Extruder+.
First, make sure you are running the latest firmware. On your printer, navigate to Info. Your printer should be running 2.6.1. If it isn't, you can follow these instructions to update it.
Next, let's investigate if there's an issue with your filament routing.