wifi assist greyed out

Wifi Assist will be greyed-out if you have already turned off Cellular (Mobile) Data

so

Turn on Cellular (Mobile) Data

Turn off Wifi Assist

Turn off Cellular (Mobile) Data if you want it on

If you have Cellular (Mobile) Data turned off anyway then there is no way that WiFi assist can operate (I would have thought - I may be wrong)

Hi! Can you decribe your question more?

As i understand, you have troubles with WI-FI?

If so, you can Reset your Networking settings by going to Settings > General > Reset > Reset Networking

Best Regards

Nicki