I encountered the same issue with my azure functions. Occasionally, I would get a 404 error when trying to access them. When I checked the Azure portal and refreshed the page, all my functions appeared to be gone almost as if they have been deleted. Redeploying the functions resolved the issue, and everything started working normally again. It was strange, but I noticed this tended to happen roughly once a month. It seems that if there are no active deployments for over a month, the functions might be completely removed from the active deployment.