Is this happening each time you deploy? Also, if the functions are not visible are they still working? As in does your http trigger still work?

I've encountered this issue before in app service; however, I was missing these two environment variables

SCM_DO_BUILD_DURING_DEPLOYMENT : true
ENABLE_ORYX_BUILD : true

here's the entire list of settings with explanation: https://learn.microsoft.com/en-us/azure/azure-functions/functions-app-settings