Impossible to export a video to GIF for web on Photoshop CC 2020

Hi there,

I've got a problem with my Photoshop CC 2020:  I've made a video in After Effect with transparent background and i want to transform it in a GIF in Photoshop. But i can't "Save for web" anymore, i already have this message : "The operation could not be completed / An unknown operating system error has occured"

I have Photoshop 21.1.2 on a iMac Catalina 10.15.4

And also, i already make this move : "the System Preferences for Mac then navigate to Security and Privacy > select the Privacy Tab > Select Accessibility from the list on the left and add Photoshop to the list. Also, grant Photoshop permissions to the Files and Folders then restart the computer to check if that helps."
But nothing change :'(

Can someone's please help me ?
thank you !