Okay, I tried deleting Itch, then re-installing it. And i also tried to restart my laptop. it didn't work. =(
Viewing post in What games can i use to publish on itch?
Im not sure if it was really an error because i didn't get any message. I uploaded it this way: Dashboard> Create new project> Upload file(s). I tried to download the game for myself and it was a c3p file. I opened it and Windows asked if i would like to use chrome to open the file, or Microsoft store.
Well, if you can't figure it out, ask in General Development. But the export command shouldn't be hard to find, it's pretty important.
However, this page from the Construct 3 manual says the export option is under Menu->Project. I just tried it online, and it's there.